feat(api): add log_request_body_enabled feature flag support

Add runtime feature flag to control whether request bodies are stored
in logs. The Handler now accepts a Redis client to check the
log_request_body_enabled feature flag before persisting log records.

- Add logRequestBodyFeatureKey constant for feature flag
- Inject Redis client into Handler for feature flag lookups
- Strip request body from log records when feature is disabled
- Update tests to pass Redis client to NewHandler

internal/api/provider_handler_test.go

@@ -36,7 +36,7 @@ func newTestHandler(t *testing.T) (*Handler, *gorm.DB) {
 	rdb := redis.NewClient(&redis.Options{Addr: mr.Addr()})
 	sync := service.NewSyncService(rdb)
 
-	return NewHandler(db, sync, nil), db
+	return NewHandler(db, sync, nil, rdb), db
 }
 
 func TestCreateProvider_DefaultsVertexLocationGlobal(t *testing.T) {