refactor: Update GitHub connector to use gitingest CLI

- Refactored GitHubConnector to utilize gitingest CLI via subprocess, improving performance and avoiding async issues with Celery.
- Updated ingestion method to handle repository digests more efficiently, including error handling for subprocess execution.
- Adjusted GitHub indexer to call the new synchronous ingestion method.
- Clarified documentation regarding the optional nature of the Personal Access Token for public repositories.

surfsense_backend/app/tasks/connector_indexers/github_indexer.py

@@ -173,8 +173,13 @@ async def index_github_repos(
             logger.info(f"Ingesting repository: {repo_full_name}")
 
             try:
-                # Ingest the entire repository
-                digest = await github_client.ingest_repository(repo_full_name)
+                # Run gitingest via subprocess (isolated from event loop)
+                # Using to_thread to not block the async database operations
+                import asyncio
+
+                digest = await asyncio.to_thread(
+                    github_client.ingest_repository, repo_full_name
+                )
 
                 if not digest:
                     logger.warning(