feat(garmin): add direct garminconnect wrapper script

Replaces mcp-garmin's server.py: a JSON-lines subprocess protocol
(authenticate/complete_mfa/call) around garminconnect directly, no MCP.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/internal/garmin/pyscript/.gitignore

@@ -0,0 +1,4 @@
+.venv/
+__pycache__/
+.pytest_cache/
+*.pyc