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/ar.json

@@ -12,6 +12,7 @@
   "Logout": "تسجيل الخروج",
   "Login": "تسجيل الدخول",
   "Providers": "الموفرون",
+  "Style": "النمط",
   "Usage": "الإحصائيات",
   "API Key": "مفتاح API",
   "Connected": "متصل",
@@ -176,6 +177,7 @@
   "How it works:": "كيف يعمل:",
   "Antigravity/Copilot IDE request → DNS redirect to localhost:443 → MITM proxy intercepts → 9Router → response to Antigravity/Copilot": "طلب Antigravity/Copilot IDE → إعادة توجيه DNS إلى localhost:443 → يعترض وكيل MITM → 9Router → الرد إلى Antigravity/Copilot",
   "No API keys — create one in Keys page": "لا توجد مفاتيح API — قم بإنشاء واحدة في صفحة المفاتيح",
+  "e.g. a warm, gentle voice, speaking slowly with a British accent": "مثال: صوت دافئ ولطيف، يتحدث ببطء بلهجة بريطانية",
   "sk_9router (default)": "sk_9router (افتراضي)",
   "Server started": "تم بدء الخادم",
   "Failed to start server": "فشل في بدء الخادم",