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/es.json

@@ -12,6 +12,7 @@
   "Logout": "Cerrar sesión",
   "Login": "Iniciar sesión",
   "Providers": "Proveedores",
+  "Style": "Estilo",
   "Usage": "Estadísticas",
   "API Key": "Clave API",
   "Connected": "Conectado",
@@ -176,6 +177,7 @@
   "How it works:": "Cómo funciona:",
   "Antigravity/Copilot IDE request → DNS redirect to localhost:443 → MITM proxy intercepts → 9Router → response to Antigravity/Copilot": "Solicitud de Antigravity/Copilot IDE → Redireccionamiento DNS a localhost:443 → El proxy MITM intercepta → 9Router → respuesta a Antigravity/Copilot",
   "No API keys — create one in Keys page": "Sin claves API — cree una en la página Claves",
+  "e.g. a warm, gentle voice, speaking slowly with a British accent": "p. ej.: voz cálida y suave, hablando lentamente con acento británico",
   "sk_9router (default)": "sk_9router (predeterminado)",
   "Server started": "Servidor iniciado",
   "Failed to start server": "Error al iniciar el servidor",