feat(api): add structured JSON access log with request-id correlation

backend/internal/config/config.go

@@ -37,6 +37,8 @@ type Config struct {
 
 	MinConfidence        float64
 	IncrementalSyncEvery time.Duration
+	// LogLevel controls internal/applog's JSON logger ("debug"|"info"|"warn"|"error").
+	LogLevel string
 
 	// OIDC login gate (Keycloak). BackendURL is this app's own externally
 	// reachable origin (e.g. "https://geniusrun.example.com") -- it derives
@@ -75,6 +77,7 @@ func Load() (Config, error) {
 		GarminTokenStoreRoot: os.Getenv("GARMIN_TOKENSTORE"),
 		MinConfidence:        getEnvFloat("GENIUSRUN_MIN_CONFIDENCE", 0.6),
 		IncrementalSyncEvery: getEnvDuration("GENIUSRUN_INCREMENTAL_SYNC_EVERY", 6*time.Hour),
+		LogLevel:             getEnvDefault("GENIUSRUN_LOG_LEVEL", "info"),
 		BackendURL:           strings.TrimRight(os.Getenv("GENIUSRUN_BACKEND_URL"), "/"),
 		OIDCIssuerURL:        os.Getenv("GENIUSRUN_OIDC_ISSUER_URL"),
 		OIDCClientID:         os.Getenv("GENIUSRUN_OIDC_CLIENT_ID"),