feat(client): add Timestamp component, ESLint 10 + Prettier, and code quality fixes

- add Timestamp component with moment relative time and ISO tooltip
- add Timestamp stories (JustNow, MinutesAgo, HoursAgo, DaysAgo, MonthsAgo)
- add ESLint 10 with typescript-eslint, react-hooks, react-refresh, prettier
- add Prettier config with singleQuote, semi, trailingComma all, printWidth 100
- add lint, lint:fix, format, test:storybook scripts to package.json
- fix react-hooks/set-state-in-effect in all page components
- auto-fix 113 Prettier formatting issues across src and .storybook

client/src/pages/SessionsPage.tsx

@@ -2,7 +2,7 @@ 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 { Badge, Button, Table, type TableColumn, Timestamp } from '../ui';
 import styles from './Page.module.css';
 
 export function SessionsPage() {
@@ -12,38 +12,39 @@ export function SessionsPage() {
   const [error, setError] = useState<string | null>(null);
 
   const load = useCallback(() => {
-    setLoading(true);
-    sessions.list()
+    sessions
+      .list()
       .then((res) => setItems(res.data))
       .catch((err: Error) => setError(err.message))
       .finally(() => setLoading(false));
   }, []);
 
-  useEffect(load, [load]);
+  useEffect(() => {
+    load();
+  }, [load]);
 
   const handleDelete = async (id: number) => {
     await sessions.remove(id);
+    setLoading(true);
     load();
   };
 
   const columns: TableColumn<Session>[] = [
-    { 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: '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: t('sessions.col_status'),
       width: 100,
       render: (s) => (
-        <Badge variant={s.status === 'open' ? 'success' : 'neutral'}>
-          {s.status}
-        </Badge>
+        <Badge variant={s.status === 'open' ? 'success' : 'neutral'}>{s.status}</Badge>
       ),
     },
     {
       key: 'lastUsed',
       header: t('sessions.col_lastUsed'),
       width: 160,
-      render: (s) => s.lastUsedAt ? new Date(s.lastUsedAt).toLocaleString() : '—',
+      render: (s) => (s.lastUsedAt ? <Timestamp value={s.lastUsedAt} /> : '—'),
     },
     {
       key: 'actions',