Refactor API handlers and proxy logic

- Centralized `getClient` logic into a dedicated function to reduce redundancy.
- Moved proxy initialization to a new utility function `SetProxy` in `internal/util/proxy.go`.
- Replaced `Internal` handler with `CLIHandler` in `server.go` for improved clarity and consistency.
- Removed unused functions and redundant HTTP client setup across the codebase for better maintainability.

internal/api/server.go

@@ -81,7 +81,7 @@ func (s *Server) setupRoutes() {
 			},
 		})
 	})
-	s.engine.POST("/v1internal:method", s.handlers.Internal)
+	s.engine.POST("/v1internal:method", s.handlers.CLIHandler)
 
 }