fix: update cognee-cli -ui MCP docker image (#1652)

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## Description
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Since standalone MCP changes were not in `cognee-mcp:main`, we had to
temporarily use custom tagged image before changes could be merged into
main.

This PR sets image to follow `cognee-mcp:main` now that the change is in
main.

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cognee/api/v1/ui/ui.py

@@ -503,7 +503,7 @@ def start_ui(
     if start_mcp:
         logger.info("Starting Cognee MCP server with Docker...")
         try:
-            image = "cognee/cognee-mcp:feature-standalone-mcp"  # TODO: change to "cognee/cognee-mcp:main" right before merging into main
+            image = "cognee/cognee-mcp:main"
             subprocess.run(["docker", "pull", image], check=True)
 
             import uuid
@@ -538,9 +538,7 @@ def start_ui(
                 env_file = os.path.join(cwd, ".env")
                 docker_cmd.extend(["--env-file", env_file])
 
-            docker_cmd.append(
-                image
-            )  # TODO: change to "cognee/cognee-mcp:main" right before merging into main
+            docker_cmd.append(image)
 
             mcp_process = subprocess.Popen(
                 docker_cmd,