feat: Integrate gitingest for GitHub repository ingestion

- Added gitingest as a dependency to streamline the ingestion of GitHub repositories.
- Refactored GitHubConnector to utilize gitingest for efficient repository digest generation, reducing API calls.
- Updated GitHub indexer to process entire repository digests, enhancing performance and simplifying the indexing process.
- Modified GitHub connect form to indicate that the Personal Access Token is optional for public repositories.

surfsense_backend/pyproject.toml

@@ -60,6 +60,7 @@ dependencies = [
     "mcp>=1.25.0",
     "starlette>=0.40.0,<0.51.0",
     "sse-starlette>=3.1.1,<3.1.2",
+    "gitingest>=0.3.1",
 ]
 
 [dependency-groups]