fix: resolve all architecture validation warnings

Service layer:
- Remove db.commit() calls from credentials_service.py (SVC-006)
- Move transaction control to API endpoint level
- Rename client.py -> client_service.py (NAM-002)
- Rename credentials.py -> credentials_service.py (NAM-002)

JavaScript:
- Use centralized logger in admin letzshop.js (JS-001)
- Replace console.log/error with LogConfig logger

Frontend templates:
- Use page_header_flex macro for page header (FE-007)
- Use error_state macro for error display (FE-003)
- Use table_wrapper macro for vendors table (FE-005)
- Use modal macro for configuration and orders modals (FE-004)

All 31 Letzshop tests pass. Architecture validation: 0 errors, 0 warnings.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/services/letzshop/__init__.py

@@ -9,14 +9,14 @@ Provides:
 - Fulfillment sync service
 """
 
-from .client import (
+from .client_service import (
     LetzshopAPIError,
     LetzshopAuthError,
     LetzshopClient,
     LetzshopClientError,
     LetzshopConnectionError,
 )
-from .credentials import (
+from .credentials_service import (
     CredentialsError,
     CredentialsNotFoundError,
     LetzshopCredentialsService,

app/services/letzshop/client_service.py

@@ -1,4 +1,4 @@
-# app/services/letzshop/client.py
+# app/services/letzshop/client_service.py
 """
 GraphQL client for Letzshop marketplace API.
 

app/services/letzshop/credentials_service.py

@@ -1,4 +1,4 @@
-# app/services/letzshop/credentials.py
+# app/services/letzshop/credentials_service.py
 """
 Letzshop credentials management service.
 
@@ -13,7 +13,7 @@ from sqlalchemy.orm import Session
 from app.utils.encryption import decrypt_value, encrypt_value, mask_api_key
 from models.database.letzshop import VendorLetzshopCredentials
 
-from .client import LetzshopClient
+from .client_service import LetzshopClient
 
 logger = logging.getLogger(__name__)
 
@@ -127,8 +127,7 @@ class LetzshopCredentialsService:
         )
 
         self.db.add(credentials)
-        self.db.commit()
-        self.db.refresh(credentials)
+        self.db.flush()
 
         logger.info(f"Created Letzshop credentials for vendor {vendor_id}")
         return credentials
@@ -168,8 +167,7 @@ class LetzshopCredentialsService:
         if sync_interval_minutes is not None:
             credentials.sync_interval_minutes = sync_interval_minutes
 
-        self.db.commit()
-        self.db.refresh(credentials)
+        self.db.flush()
 
         logger.info(f"Updated Letzshop credentials for vendor {vendor_id}")
         return credentials
@@ -189,7 +187,7 @@ class LetzshopCredentialsService:
             return False
 
         self.db.delete(credentials)
-        self.db.commit()
+        self.db.flush()
 
         logger.info(f"Deleted Letzshop credentials for vendor {vendor_id}")
         return True
@@ -370,8 +368,7 @@ class LetzshopCredentialsService:
         credentials.last_sync_status = status
         credentials.last_sync_error = error
 
-        self.db.commit()
-        self.db.refresh(credentials)
+        self.db.flush()
 
         return credentials