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)

.env.example

@@ -14,6 +14,10 @@ NODE_ENV=production
 API_KEY_SECRET=endpoint-proxy-api-key-secret
 MACHINE_ID_SALT=endpoint-proxy-salt
 ENABLE_REQUEST_LOGS=false
+# Console verbosity: DEBUG | INFO | WARN | ERROR. Default INFO. In production set
+# ERROR to only print important errors (hides ▶ POST / 📊 DONE / [COMBO] / [CHAT]).
+# Can also be changed at runtime from dashboard Settings → Logging.
+# LOG_LEVEL=ERROR
 OBSERVABILITY_ENABLED=true
 AUTH_COOKIE_SECURE=false
 REQUIRE_API_KEY=false
@@ -34,5 +38,8 @@ NEXT_PUBLIC_CLOUD_URL=https://9router.com
 # ALL_PROXY=socks5://127.0.0.1:7890
 # NO_PROXY=localhost,127.0.0.1
 
+# Optional SearXNG endpoint for the built-in unauthenticated web-search provider.
+# SEARXNG_URL=http://searxng:8080/search
+
 # Currently unused by application runtime (kept as reference)
 # INSTANCE_NAME=9router