feat(gitea): migrate to published gitea-mcp package from Gitea PyPI

mcp-servers/gitea/ thinned to venv wrapper — source code removed,
package installed from registry. run.sh updated from mcp_server.server
to gitea_mcp.server. requirements.txt points to Gitea PyPI.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

mcp-servers/gitea/run.sh

@@ -17,5 +17,4 @@ else
 fi
 
 cd "$SCRIPT_DIR"
-export PYTHONPATH="$SCRIPT_DIR"
-exec "$PYTHON" -m mcp_server.server "$@"
+exec "$PYTHON" -m gitea_mcp.server "$@"