chore: wire up the new garmin.Config shape, refresh start.sh and CLAUDE.md

Removes the last references to garmin.Config.ServerPath and the
MCP_GARMIN_* env vars now that the wrapper script is embedded in the
binary; updates CLAUDE.md's mcp-garmin section to describe the direct
wrapper instead.

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

backend/internal/api/server.go

@@ -34,7 +34,7 @@ type Server struct {
 	// *mock.Client (see newTestServer in api_test.go).
 	GarminFactory func(garmin.Config) garmin.Client
 	// GarminBase holds the plumbing shared by every user's garmin.Config
-	// (subprocess paths + the token-store root directory); only
+	// (the python interpreter path + the token-store root directory); only
 	// GarminEmail/GarminPassword/TokenStorePath vary per user, filled in by
 	// garminFor.
 	GarminBase garmin.Config