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/nl.json

@@ -12,6 +12,7 @@
   "Logout": "Afmelden",
   "Login": "Aanmelden",
   "Providers": "Providers",
+  "Style": "Stijl",
   "Usage": "Statistieken",
   "API Key": "API-sleutel",
   "Connected": "Verbonden",
@@ -176,6 +177,7 @@
   "How it works:": "Hoe het werkt:",
   "Antigravity/Copilot IDE request → DNS redirect to localhost:443 → MITM proxy intercepts → 9Router → response to Antigravity/Copilot": "Antigravity/Copilot IDE-aanvraag → DNS-omleiding naar localhost:443 → MITM-proxy onderschept → 9Router → antwoord naar Antigravity/Copilot",
   "No API keys — create one in Keys page": "Geen API-sleutels — maak er één aan op de pagina Sleutels",
+  "e.g. a warm, gentle voice, speaking slowly with a British accent": "bijv.: een warme, zachte stem, die langzaam praat met een Brits accent",
   "sk_9router (default)": "sk_9router (standaard)",
   "Server started": "Server gestart",
   "Failed to start server": "Server starten mislukt",