feat: enhance completion service with session management and language support

- Introduced session management using Redis for tracking active sessions.
- Added session claiming and releasing functionality in the completion manager.
- Enhanced HTTP and WebSocket completion endpoints to support multiple languages.
- Implemented request timeout and maximum body size configurations for API routes.
- Updated client-side code to handle session IDs and language parameters in completion requests.
- Improved error handling for unsupported languages and session conflicts.
- Added tests for the completion manager to ensure proper session handling and cleanup.

backend/go.mod

@@ -5,12 +5,15 @@ go 1.25
 require (
 	github.com/gin-gonic/gin v1.11.0
 	github.com/gorilla/websocket v1.5.3
+	github.com/redis/go-redis/v9 v9.17.3
 )
 
 require (
 	github.com/bytedance/sonic v1.14.0 // indirect
 	github.com/bytedance/sonic/loader v0.3.0 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/cloudwego/base64x v0.1.6 // indirect
+	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
 	github.com/gabriel-vasile/mimetype v1.4.8 // indirect
 	github.com/gin-contrib/sse v1.1.0 // indirect
 	github.com/go-playground/locales v0.14.1 // indirect