fix(translate): Kilo API response_format, reasoning_effort skip, structured_outputs fallback, refusal handling

- Enable response_format (json_object) for all providers including Kilo/OpenRouter
- Skip reasoning_effort for Kilo/OpenRouter (returns 400 — mandatory reasoning)
- Add structured_outputs fallback: retry once without response_format if upstream
  provider (e.g. StepFun) rejects it with 'structured_outputs is not supported'
- Handle model refusal field (refusal) instead of treating as empty content
- Fix None-handling guards for message/finish_reason/content fields
- Apply same fixes to both preview.py and executor.py _call_openai_compatible
- Connect orphaned TermCorrectionPopup, BulkReplaceModal, BulkCorrectionSidebar

docker/nginx.conf

@@ -16,6 +16,7 @@ server {
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_read_timeout 300s;
     }
 
     location /ws/ {
@@ -27,5 +28,6 @@ server {
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_read_timeout 300s;
     }
 }