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/.storybook/preview.tsx

@@ -1,6 +1,6 @@
-import React from 'react'
-import type { Preview } from '@storybook/react-vite'
-import '../src/ui/tokens.css'
+import React from 'react';
+import type { Preview } from '@storybook/react-vite';
+import '../src/ui/tokens.css';
 
 const preview: Preview = {
   globalTypes: {
@@ -12,7 +12,7 @@ const preview: Preview = {
         icon: 'circlehollow',
         items: [
           { value: 'light', icon: 'sun', title: 'Light' },
-          { value: 'dark',  icon: 'moon', title: 'Dark' },
+          { value: 'dark', icon: 'moon', title: 'Dark' },
         ],
         dynamicTitle: true,
       },
@@ -20,13 +20,13 @@ const preview: Preview = {
   },
   decorators: [
     (Story, context) => {
-      const theme = (context.globals['theme'] as string) ?? 'light'
-      document.documentElement.setAttribute('data-theme', theme)
+      const theme = (context.globals['theme'] as string) ?? 'light';
+      document.documentElement.setAttribute('data-theme', theme);
       return (
         <div style={{ background: 'var(--color-bg)', minHeight: '100vh', padding: 0 }}>
           <Story />
         </div>
-      )
+      );
     },
   ],
   parameters: {
@@ -40,6 +40,6 @@ const preview: Preview = {
       test: 'todo',
     },
   },
-}
+};
 
-export default preview
+export default preview;