feat: Implement ZIP RAG import functionality with background processing

- Added support for ZIP RAG import in the asset management system.
- Introduced a new background task type for ZIP RAG imports.
- Enhanced the asset import process to allow for optional development processing.
- Updated the UI to reflect the new RAG processing status and options.
- Created database migration for background tasks related to ZIP RAG imports.
- Refactored asset handling to support FLV normalization and improved error handling.
- Added new API endpoints and updated existing ones to accommodate changes.

nginx/studio.conf

@@ -3,11 +3,30 @@
 
 # Allow large ZIP uploads (RAG bulk import can exceed 2GB).
 client_max_body_size 4096m;
-client_body_timeout 1800s;
+client_body_timeout 43200s;
 
 # API routes that need to go to port 3001
 # Prefer the explicit `/cms-api/*` prefix for frontend fetches. This avoids collisions
 # with Next.js pages like `/courses` and `/admin` that share the same host.
+location = /cms-api/api/assets/import-zip {
+    # Upload/import of large ZIPs can run for several minutes.
+    # Keep this route unbuffered and with very high upstream timeouts.
+    rewrite ^/cms-api/(.*)$ /$1 break;
+    proxy_pass http://openccb-studio:3001;
+    proxy_request_buffering off;
+    proxy_buffering off;
+    proxy_set_header Host $host;
+    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 $http_x_forwarded_proto;
+    proxy_set_header Connection "";
+    proxy_http_version 1.1;
+    proxy_connect_timeout 7200s;
+    proxy_send_timeout 43200s;
+    proxy_read_timeout 43200s;
+    send_timeout 43200s;
+}
+
 location /cms-api/ {
     # CORS safety net at proxy level for CMS API.
     set $cors_origin "";
@@ -42,9 +61,9 @@ location /cms-api/ {
     proxy_set_header Connection "";
     proxy_http_version 1.1;
     proxy_connect_timeout 300s;
-    proxy_send_timeout 7200s;
-    proxy_read_timeout 7200s;
-    send_timeout 7200s;
+    proxy_send_timeout 43200s;
+    proxy_read_timeout 43200s;
+    send_timeout 43200s;
 }
 
 location /lms-api/ {