fix: resolve cross-module import violations with lazy import pattern

- Convert core→optional imports to lazy imports with try/except fallbacks
- cms/media_service: use TYPE_CHECKING for ProductMedia type hints
- customers/customer_service: wrap Order imports in try/except
- tenancy/admin_platform_users: wrap stats_service import in try/except
- Enhance validate_architecture.py to recognize lazy import patterns
- Add module_dependency_graph.py script for dependency visualization

The lazy import pattern allows optional modules to be truly optional while
maintaining type safety through TYPE_CHECKING blocks.

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

app/modules/cms/services/media_service.py

@@ -16,10 +16,14 @@ import shutil
 import uuid
 from datetime import UTC, datetime
 from pathlib import Path
+from typing import TYPE_CHECKING, Any
 
 from sqlalchemy import or_
 from sqlalchemy.orm import Session
 
+if TYPE_CHECKING:
+    from app.modules.catalog.models import ProductMedia
+
 from app.modules.cms.exceptions import (
     MediaNotFoundException,
     MediaUploadException,
@@ -28,7 +32,6 @@ from app.modules.cms.exceptions import (
     MediaFileTooLargeException,
 )
 from app.modules.cms.models import MediaFile
-from app.modules.catalog.models import ProductMedia
 
 logger = logging.getLogger(__name__)
 
@@ -454,7 +457,7 @@ class MediaService:
         product_id: int,
         usage_type: str = "gallery",
         display_order: int = 0,
-    ) -> ProductMedia:
+    ) -> "ProductMedia | None":
         """
         Attach a media file to a product.
 
@@ -467,8 +470,14 @@ class MediaService:
             display_order: Order for galleries
 
         Returns:
-            Created ProductMedia association
+            Created ProductMedia association, or None if catalog module unavailable
         """
+        try:
+            from app.modules.catalog.models import ProductMedia
+        except ImportError:
+            logger.warning("Catalog module not available for media-product attachment")
+            return None
+
         # Verify media belongs to vendor
         media = self.get_media(db, vendor_id, media_id)
 
@@ -524,8 +533,14 @@ class MediaService:
             usage_type: Specific usage type to remove (None = all)
 
         Returns:
-            True if detached
+            True if detached, False if catalog module unavailable
         """
+        try:
+            from app.modules.catalog.models import ProductMedia
+        except ImportError:
+            logger.warning("Catalog module not available for media-product detachment")
+            return False
+
         # Verify media belongs to vendor
         media = self.get_media(db, vendor_id, media_id)