feat(client): add i18n with i18next and react-i18next

- install i18next and react-i18next
- create src/i18n/index.ts bootstrapping i18next with initReactI18next
- add src/i18n/locales/en.json with keys for nav, all pages, and ThemeSwitcher
- replace hardcoded English strings in App, all pages, and ThemeSwitcher with t()
- move static column definitions inside components where useTranslation is available

client/src/App.tsx

@@ -5,18 +5,22 @@ import { KeysPage } from './pages/KeysPage';
 import { SessionsPage } from './pages/SessionsPage';
 import { ScenariosPage } from './pages/ScenariosPage';
 import { useState } from 'react';
+import { useTranslation } from 'react-i18next';
 
 type Section = 'environments' | 'keys' | 'sessions' | 'scenarios';
 
-const NAV: { id: Section; label: string }[] = [
-  { id: 'environments', label: 'Environments' },
-  { id: 'keys',         label: 'Keys' },
-  { id: 'sessions',     label: 'Sessions' },
-  { id: 'scenarios',    label: 'Scenarios' },
-];
+
 
 export default function App() {
   const [active, setActive] = useState<Section>('scenarios');
+  const { t } = useTranslation();
+
+  const NAV: { id: Section; label: string }[] = [
+    { id: 'environments', label: t('nav.environments') },
+    { id: 'keys',         label: t('nav.keys') },
+    { id: 'sessions',     label: t('nav.sessions') },
+    { id: 'scenarios',    label: t('nav.scenarios') },
+  ];
 
   return (
     <div className={styles.shell}>

client/src/i18n/index.ts

@@ -0,0 +1,14 @@
+import i18n from 'i18next';
+import { initReactI18next } from 'react-i18next';
+import en from './locales/en.json';
+
+i18n
+  .use(initReactI18next)
+  .init({
+    resources: { en: { translation: en } },
+    lng: 'en',
+    fallbackLng: 'en',
+    interpolation: { escapeValue: false },
+  });
+
+export default i18n;

client/src/i18n/locales/en.json

@@ -0,0 +1,45 @@
+{
+  "nav": {
+    "environments": "Environments",
+    "keys": "Keys",
+    "sessions": "Sessions",
+    "scenarios": "Scenarios"
+  },
+  "environments": {
+    "title": "Environments",
+    "col_id": "ID",
+    "col_name": "Name",
+    "col_urls": "URLs",
+    "col_updated": "Updated",
+    "empty": "No environments yet."
+  },
+  "keys": {
+    "title": "Keys",
+    "col_name": "Key name",
+    "empty": "No key files found."
+  },
+  "sessions": {
+    "title": "Sessions",
+    "col_id": "ID",
+    "col_name": "Name",
+    "col_status": "Status",
+    "col_lastUsed": "Last Used",
+    "empty": "No sessions yet.",
+    "action_delete": "Delete"
+  },
+  "scenarios": {
+    "title": "Scenarios",
+    "col_id": "ID",
+    "col_name": "Name",
+    "col_updated": "Updated",
+    "empty": "No scenarios yet.",
+    "action_run": "Run",
+    "action_delete": "Delete"
+  },
+  "theme": {
+    "switch_to_light": "Switch to light theme",
+    "switch_to_dark": "Switch to dark theme",
+    "light_mode": "Light mode",
+    "dark_mode": "Dark mode"
+  }
+}

client/src/main.tsx

@@ -1,5 +1,6 @@
 import { StrictMode } from 'react'
 import { createRoot } from 'react-dom/client'
+import './i18n'
 import './ui/tokens.css'
 import App from './App'
 

client/src/pages/EnvironmentsPage.tsx

@@ -1,34 +1,36 @@
 import { useEffect, useState } from 'react';
+import { useTranslation } from 'react-i18next';
 import { environments } from '../api';
 import type { Environment } from '../api';
 import { Table, type TableColumn } from '../ui';
 import styles from './Page.module.css';
 
-const columns: TableColumn<Environment>[] = [
-  { key: 'id',      header: 'ID',      render: (e) => e.id,   width: 60 },
-  { key: 'name',    header: 'Name',    render: (e) => e.name },
-  {
-    key: 'urls',
-    header: 'URLs',
-    render: (e) =>
-      Object.entries(e.urls)
-        .filter(([, v]) => v)
-        .map(([k, v]) => `${k}: ${v}`)
-        .join(' · ') || '—',
-  },
-  {
-    key: 'updated',
-    header: 'Updated',
-    width: 120,
-    render: (e) => new Date(e.updatedAt).toLocaleDateString(),
-  },
-];
-
 export function EnvironmentsPage() {
+  const { t } = useTranslation();
   const [items, setItems] = useState<Environment[]>([]);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
 
+  const columns: TableColumn<Environment>[] = [
+    { key: 'id',      header: t('environments.col_id'),      render: (e) => e.id,   width: 60 },
+    { key: 'name',    header: t('environments.col_name'),    render: (e) => e.name },
+    {
+      key: 'urls',
+      header: t('environments.col_urls'),
+      render: (e) =>
+        Object.entries(e.urls)
+          .filter(([, v]) => v)
+          .map(([k, v]) => `${k}: ${v}`)
+          .join(' · ') || '—',
+    },
+    {
+      key: 'updated',
+      header: t('environments.col_updated'),
+      width: 120,
+      render: (e) => new Date(e.updatedAt).toLocaleDateString(),
+    },
+  ];
+
   useEffect(() => {
     setLoading(true);
     environments.list()
@@ -39,14 +41,14 @@ export function EnvironmentsPage() {
 
   return (
     <div>
-      <h1 className={styles.heading}>Environments</h1>
+      <h1 className={styles.heading}>{t('environments.title')}</h1>
       {error && <p className={styles.error}>{error}</p>}
       <Table
         columns={columns}
         data={items}
         rowKey={(e) => e.id}
         loading={loading}
-        emptyMessage="No environments yet."
+        emptyMessage={t('environments.empty')}
       />
     </div>
   );

client/src/pages/KeysPage.tsx

@@ -1,19 +1,21 @@
 import { useEffect, useState } from 'react';
+import { useTranslation } from 'react-i18next';
 import { keys } from '../api';
 import { Table, type TableColumn } from '../ui';
 import styles from './Page.module.css';
 
 interface KeyRow { name: string }
 
-const columns: TableColumn<KeyRow>[] = [
-  { key: 'name', header: 'Key name', render: (k) => k.name },
-];
-
 export function KeysPage() {
+  const { t } = useTranslation();
   const [items, setItems] = useState<KeyRow[]>([]);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
 
+  const columns: TableColumn<KeyRow>[] = [
+    { key: 'name', header: t('keys.col_name'), render: (k) => k.name },
+  ];
+
   useEffect(() => {
     setLoading(true);
     keys.list()
@@ -24,14 +26,14 @@ export function KeysPage() {
 
   return (
     <div>
-      <h1 className={styles.heading}>Keys</h1>
+      <h1 className={styles.heading}>{t('keys.title')}</h1>
       {error && <p className={styles.error}>{error}</p>}
       <Table
         columns={columns}
         data={items}
         rowKey={(k) => k.name}
         loading={loading}
-        emptyMessage="No key files found."
+        emptyMessage={t('keys.empty')}
       />
     </div>
   );

client/src/pages/ScenariosPage.tsx

@@ -1,10 +1,12 @@
 import { useCallback, useEffect, useState } from 'react';
+import { useTranslation } from 'react-i18next';
 import { scenarios } from '../api';
 import type { Scenario } from '../api';
 import { Button, Table, type TableColumn } from '../ui';
 import styles from './Page.module.css';
 
 export function ScenariosPage() {
+  const { t } = useTranslation();
   const [items, setItems] = useState<Scenario[]>([]);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
@@ -29,11 +31,11 @@ export function ScenariosPage() {
   };
 
   const columns: TableColumn<Scenario>[] = [
-    { key: 'id',      header: 'ID',      render: (s) => s.id,   width: 60 },
-    { key: 'name',    header: 'Name',    render: (s) => s.name },
+    { key: 'id',      header: t('scenarios.col_id'),      render: (s) => s.id,   width: 60 },
+    { key: 'name',    header: t('scenarios.col_name'),    render: (s) => s.name },
     {
       key: 'updated',
-      header: 'Updated',
+      header: t('scenarios.col_updated'),
       width: 120,
       render: (s) => new Date(s.updatedAt).toLocaleDateString(),
     },
@@ -44,8 +46,8 @@ export function ScenariosPage() {
       align: 'right',
       render: (s) => (
         <span style={{ display: 'inline-flex', gap: 6 }}>
-          <Button size="sm" onClick={() => handleRun(s.id)}>Run</Button>
-          <Button variant="secondary" size="sm" onClick={() => handleDelete(s.id)}>Delete</Button>
+          <Button size="sm" onClick={() => handleRun(s.id)}>{t('scenarios.action_run')}</Button>
+          <Button variant="secondary" size="sm" onClick={() => handleDelete(s.id)}>{t('scenarios.action_delete')}</Button>
         </span>
       ),
     },
@@ -53,14 +55,14 @@ export function ScenariosPage() {
 
   return (
     <div>
-      <h1 className={styles.heading}>Scenarios</h1>
+      <h1 className={styles.heading}>{t('scenarios.title')}</h1>
       {error && <p className={styles.error}>{error}</p>}
       <Table
         columns={columns}
         data={items}
         rowKey={(s) => s.id}
         loading={loading}
-        emptyMessage="No scenarios yet."
+        emptyMessage={t('scenarios.empty')}
       />
     </div>
   );

client/src/pages/SessionsPage.tsx

@@ -1,10 +1,12 @@
 import { useCallback, useEffect, useState } from 'react';
+import { useTranslation } from 'react-i18next';
 import { sessions } from '../api';
 import type { Session } from '../api';
 import { Badge, Button, Table, type TableColumn } from '../ui';
 import styles from './Page.module.css';
 
 export function SessionsPage() {
+  const { t } = useTranslation();
   const [items, setItems] = useState<Session[]>([]);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
@@ -25,11 +27,11 @@ export function SessionsPage() {
   };
 
   const columns: TableColumn<Session>[] = [
-    { key: 'id',      header: 'ID',       render: (s) => s.id,          width: 60 },
-    { key: 'name',    header: 'Name',     render: (s) => s.sessionName },
+    { key: 'id',      header: t('sessions.col_id'),       render: (s) => s.id,          width: 60 },
+    { key: 'name',    header: t('sessions.col_name'),     render: (s) => s.sessionName },
     {
       key: 'status',
-      header: 'Status',
+      header: t('sessions.col_status'),
       width: 100,
       render: (s) => (
         <Badge variant={s.status === 'open' ? 'success' : 'neutral'}>
@@ -39,7 +41,7 @@ export function SessionsPage() {
     },
     {
       key: 'lastUsed',
-      header: 'Last Used',
+      header: t('sessions.col_lastUsed'),
       width: 160,
       render: (s) => s.lastUsedAt ? new Date(s.lastUsedAt).toLocaleString() : '—',
     },
@@ -50,7 +52,7 @@ export function SessionsPage() {
       align: 'right',
       render: (s) => (
         <Button variant="secondary" size="sm" onClick={() => handleDelete(s.id)}>
-          Delete
+          {t('sessions.action_delete')}
         </Button>
       ),
     },
@@ -58,14 +60,14 @@ export function SessionsPage() {
 
   return (
     <div>
-      <h1 className={styles.heading}>Sessions</h1>
+      <h1 className={styles.heading}>{t('sessions.title')}</h1>
       {error && <p className={styles.error}>{error}</p>}
       <Table
         columns={columns}
         data={items}
         rowKey={(s) => s.id}
         loading={loading}
-        emptyMessage="No sessions yet."
+        emptyMessage={t('sessions.empty')}
       />
     </div>
   );

client/src/ui/ThemeSwitcher/ThemeSwitcher.tsx

@@ -1,16 +1,18 @@
 import { Sun, Moon } from 'lucide-react';
+import { useTranslation } from 'react-i18next';
 import { useTheme } from '../../hooks/useTheme';
 import styles from './ThemeSwitcher.module.css';
 
 export function ThemeSwitcher() {
   const { theme, toggleTheme } = useTheme();
+  const { t } = useTranslation();
 
   return (
     <button
       className={styles.btn}
       onClick={toggleTheme}
-      aria-label={theme === 'dark' ? 'Switch to light theme' : 'Switch to dark theme'}
-      title={theme === 'dark' ? 'Light mode' : 'Dark mode'}
+      aria-label={theme === 'dark' ? t('theme.switch_to_light') : t('theme.switch_to_dark')}
+      title={theme === 'dark' ? t('theme.light_mode') : t('theme.dark_mode')}
     >
       {theme === 'dark' ? <Sun size={16} /> : <Moon size={16} />}
     </button>