refactor(pages): one about page per language, no R2 cache by default

- app/[lang]/about/page.tsx renders en, zh and ja (zh-Hant falls back
  to zh) from one JSX tree with per-language texts and generateMetadata;
  delete the cn/ and ja/ copies and redirect their old URLs
- app/[lang]/layout.tsx: use hasLocale, an OG locale table, and real
  zh/ja title and description
- components/icons/github.tsx replaces react-icons and lucide's
  deprecated Github icon
- quota-limit-toast: read the dictionary keys directly, shadow-float
- Cloudflare: defineCloudflareConfig({}) without R2, no r2_buckets, no
  dev-time OpenNext init, cf-typegen script removed,
  @opennextjs/cloudflare moves to devDependencies, docs updated

package.json

@@ -17,7 +17,6 @@
         "preview": "opennextjs-cloudflare build && opennextjs-cloudflare preview",
         "deploy": "opennextjs-cloudflare build && opennextjs-cloudflare deploy",
         "upload": "opennextjs-cloudflare build && opennextjs-cloudflare upload",
-        "cf-typegen": "wrangler types --env-interface CloudflareEnv cloudflare-env.d.ts",
         "electron:dev": "node scripts/electron-dev.mjs",
         "electron:build": "npm run build && npm run electron:compile",
         "electron:compile": "npx esbuild electron/main/index.ts electron/preload/index.ts --bundle --platform=node --outdir=dist-electron --external:electron --sourcemap",
@@ -51,7 +50,6 @@
         "@langfuse/otel": "^4.4.4",
         "@langfuse/tracing": "^4.4.9",
         "@next/third-parties": "^16.0.6",
-        "@opennextjs/cloudflare": "^1.17.1",
         "@openrouter/ai-sdk-provider": "^2.10.0",
         "@opentelemetry/api": "^1.9.0",
         "@opentelemetry/exporter-trace-otlp-http": "^0.222.0",
@@ -83,7 +81,6 @@
         "prism-react-renderer": "^2.4.1",
         "react": "^19.1.2",
         "react-dom": "^19.1.2",
-        "react-icons": "^5.5.0",
         "react-markdown": "^10.1.0",
         "saxes": "^6.0.0",
         "server-only": "^0.0.1",
@@ -108,6 +105,7 @@
     },
     "devDependencies": {
         "@biomejs/biome": "2.5.15",
+        "@opennextjs/cloudflare": "^1.17.1",
         "@playwright/test": "^1.57.0",
         "@tailwindcss/postcss": "^4",
         "@tailwindcss/typography": "^0.5.19",