feat(i18n): Integrate next-intl, localize core UI, add regional locales and zh-TW Discover sources

**Overview**
- Integrates next-intl (App Router, no i18n routing) with cookie-based locale and Accept-Language fallback.
- Adds message bundles and regional variants; sets en-US as the default.

**Key changes**
- i18n foundation
  - Adds request-scoped config to load messages per locale and injects NextIntlClientProvider in [layout.tsx]
  - Adds/updates messages for: en-US, en-GB, zh-TW, zh-HK, zh-CN, ja, ko, fr-FR, fr-CA, de.
Centralizes LOCALES, LOCALE_LABELS, and DEFAULT_LOCALE in [locales.ts]
  - Adds LocaleSwitcher (cookie-based) and [LocaleBootstrap]

- Pages and components
  - Localizes Sidebar, Home (including metadata/manifest), Settings, Discover, Library.
  - Localizes common components: MessageInput, Attach, Focus, Optimization, MessageBox, MessageSources, SearchImages, SearchVideos, EmptyChat, NewsArticleWidget, WeatherWidget.

- APIs
  - Weather API returns localized condition strings server-side.

- UX and quality
  - Converts all remaining <img> to Next Image.
  - Updates browserslist/caniuse DB to silence warnings.
  - Security: Settings API Key inputs are now password fields and placeholders were removed.

src/app/api/discover/route.ts

@@ -1,4 +1,5 @@
 import { searchSearxng } from '@/lib/searxng';
+import { getLocale } from 'next-intl/server';
 
 const websitesForTopic = {
   tech: {
@@ -37,6 +38,10 @@ export const GET = async (req: Request) => {
 
     let data = [];
 
+    // derive base language from current locale (e.g., zh-TW -> zh)
+    const locale = await getLocale();
+    const searxLanguage = 'en';
+
     if (mode === 'normal') {
       const seenUrls = new Set();
 
@@ -46,9 +51,9 @@ export const GET = async (req: Request) => {
             selectedTopic.query.map(async (query) => {
               return (
                 await searchSearxng(`site:${link} ${query}`, {
-                  engines: ['bing news'],
+                  engines: ['google news', 'bing news'],
                   pageno: 1,
-                  language: 'en',
+                  language: searxLanguage,
                 })
               ).results;
             }),
@@ -68,9 +73,9 @@ export const GET = async (req: Request) => {
         await searchSearxng(
           `site:${selectedTopic.links[Math.floor(Math.random() * selectedTopic.links.length)]} ${selectedTopic.query[Math.floor(Math.random() * selectedTopic.query.length)]}`,
           {
-            engines: ['bing news'],
+            engines: ['google news', 'bing news'],
             pageno: 1,
-            language: 'en',
+            language: searxLanguage,
           },
         )
       ).results;