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/anthropic.js

@@ -1,5 +1,3 @@
-import { CLAUDE_API_HEADERS } from "../shared.js";
-
 export default {
   id: "anthropic",
   priority: 30,
@@ -19,7 +17,7 @@ export default {
     baseUrl: "https://api.anthropic.com/v1/messages",
     format: "claude",
     headers: {
-      "Anthropic-Version": "2023-06-01",
+      "anthropic-version": "2023-06-01",
       "Anthropic-Beta": "claude-code-20250219,interleaved-thinking-2025-05-14",
     },
   },