Merge remote-tracking branch 'origin/master' into gitea/feature/end

Resolved conflicts taking origin/master (v0.5.55) as canonical, with local
features re-applied:
- runtime log level (LOG_LEVEL env + dashboard Settings → Logging, applied
  immediately and persisted across restarts)
- free/noAuth provider enable/disable toggle via providerStrategies.enabled
- parallel model testing (Test All Models / Test Selected Keys)

public/i18n/literals/zh-TW.json

@@ -12,6 +12,7 @@
   "Logout": "登出",
   "Login": "登錄",
   "Providers": "提供者",
+  "Style": "風格",
   "Usage": "統計",
   "API Key": "API 金鑰",
   "Connected": "已連接",
@@ -176,6 +177,7 @@
   "How it works:": "工作原理：",
   "Antigravity/Copilot IDE request → DNS redirect to localhost:443 → MITM proxy intercepts → 9Router → response to Antigravity/Copilot": "Antigravity/Copilot IDE 請求 → DNS 重定向到 localhost:443 → MITM 代理攔截 → 9Router → 响應到 Antigravity/Copilot",
   "No API keys — create one in Keys page": "沒有 API 金鑰 — 在金鑰頁面中創建一個",
+  "e.g. a warm, gentle voice, speaking slowly with a British accent": "例如：溫暖柔和的嗓音，用英式口音緩慢說話",
   "sk_9router (default)": "sk_9router（默認）",
   "Server started": "服務器已啟動",
   "Failed to start server": "啟動服務器失敗",