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)

open-sse/providers/registry/deepseek.js

@@ -48,4 +48,8 @@ export default {
     { id: "deepseek-chat", name: "DeepSeek V3.2 Chat" },
     { id: "deepseek-reasoner", name: "DeepSeek V3.2 Reasoner" },
   ],
+  features: {
+    usage: true,
+    usageApikey: true,
+  },
 };