Fix: replace stdout prints with debug logging (#25931)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

api/celery_entrypoint.py

 
 
 def _log(message: str):
-    print(message, flush=True)
+    _logger.debug(message)
 
 
 # grpc gevent

api/commands.py

                 if jina_plugin_id not in installed_plugins_ids:
                     if jina_plugin_unique_identifier:
                         # install jina plugin
-                        print(jina_plugin_unique_identifier)
+                        logger.debug("Installing Jina plugin %s", jina_plugin_unique_identifier)
                         PluginService.install_from_marketplace_pkg(tenant_id, [jina_plugin_unique_identifier])
 
                 auth_count = 0

api/core/schemas/registry.py

 import json
+import logging
 import threading
 from collections.abc import Mapping, MutableMapping
 from pathlib import Path
 class SchemaRegistry:
     """Schema registry manages JSON schemas with version support"""
 
+    logger: ClassVar[logging.Logger] = logging.getLogger(__name__)
+
     _default_instance: ClassVar[Optional["SchemaRegistry"]] = None
     _lock: ClassVar[threading.Lock] = threading.Lock()
 
             self.metadata[uri] = metadata
 
         except (OSError, json.JSONDecodeError) as e:
-            print(f"Warning: failed to load schema {version}/{schema_name}: {e}")
+            self.logger.warning("Failed to load schema %s/%s: %s", version, schema_name, e)
 
     def get_schema(self, uri: str) -> Any | None:
         """Retrieves a schema by URI with version support"""

api/services/rag_pipeline/rag_pipeline_transform_service.py

 import json
+import logging
 from datetime import UTC, datetime
 from pathlib import Path
 from uuid import uuid4
 from services.plugin.plugin_migration import PluginMigration
 from services.plugin.plugin_service import PluginService
 
+logger = logging.getLogger(__name__)
+
 
 class RagPipelineTransformService:
     def transform_dataset(self, dataset_id: str):
                     if plugin_unique_identifier:
                         need_install_plugin_unique_identifiers.append(plugin_unique_identifier)
         if need_install_plugin_unique_identifiers:
-            print(need_install_plugin_unique_identifiers)
+            logger.debug("Installing missing pipeline plugins %s", need_install_plugin_unique_identifiers)
             PluginService.install_from_marketplace_pkg(tenant_id, need_install_plugin_unique_identifiers)
 
     def _transfrom_to_empty_pipeline(self, dataset: Dataset):