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/cmd/geniusrund/main.go

@@ -44,7 +44,6 @@ func main() {
 
 	server := api.NewServer(db, garmin.NewClient, garmin.Config{
 		PythonPath:     cfg.GarminPythonPath,
-		ServerPath:     cfg.GarminServerPath,
 		TokenStorePath: cfg.GarminTokenStoreRoot,
 	}, appsync.Config{
 		MinConfidence: cfg.MinConfidence,