refactor(arch): use CustomerContext schema for dependency injection

Phase 5 of storefront restructure plan - fix direct model imports in
API routes by using schemas for dependency injection.

Created CustomerContext schema:
- Lightweight Pydantic model for customer data in API routes
- Populated from Customer DB model in auth dependency
- Contains all fields needed by storefront routes
- Includes from_db_model() factory method

Updated app/api/deps.py:
- _validate_customer_token now returns CustomerContext instead of Customer
- Updated docstrings for all customer auth functions

Updated module storefront routes:
- customers: Uses CustomerContext for profile/address endpoints
- orders: Uses CustomerContext for order history endpoints
- checkout: Uses CustomerContext for order placement
- messaging: Uses CustomerContext for messaging endpoints

This enforces the layered architecture (Routes → Services → Models)
by ensuring API routes never import database models directly.

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

app/modules/messaging/routes/api/storefront.py

@@ -33,6 +33,7 @@ from app.exceptions import (
     ConversationNotFoundException,
     VendorNotFoundException,
 )
+from app.modules.customers.schemas import CustomerContext
 from app.modules.messaging.models.message import ConversationType, ParticipantType
 from app.modules.messaging.schemas import (
     ConversationDetailResponse,
@@ -45,7 +46,6 @@ from app.modules.messaging.services import (
     message_attachment_service,
     messaging_service,
 )
-from models.database.customer import Customer
 
 router = APIRouter()
 logger = logging.getLogger(__name__)
@@ -74,7 +74,7 @@ def list_conversations(
     skip: int = Query(0, ge=0),
     limit: int = Query(50, ge=1, le=100),
     status: Optional[str] = Query(None, pattern="^(open|closed)$"),
-    customer: Customer = Depends(get_current_customer_api),
+    customer: CustomerContext = Depends(get_current_customer_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -146,7 +146,7 @@ def list_conversations(
 @router.get("/messages/unread-count", response_model=UnreadCountResponse)
 def get_unread_count(
     request: Request,
-    customer: Customer = Depends(get_current_customer_api),
+    customer: CustomerContext = Depends(get_current_customer_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -171,7 +171,7 @@ def get_unread_count(
 def get_conversation(
     request: Request,
     conversation_id: int = Path(..., description="Conversation ID", gt=0),
-    customer: Customer = Depends(get_current_customer_api),
+    customer: CustomerContext = Depends(get_current_customer_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -261,7 +261,7 @@ async def send_message(
     conversation_id: int = Path(..., description="Conversation ID", gt=0),
     content: str = Form(..., min_length=1, max_length=10000),
     attachments: List[UploadFile] = File(default=[]),
-    customer: Customer = Depends(get_current_customer_api),
+    customer: CustomerContext = Depends(get_current_customer_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -359,7 +359,7 @@ async def send_message(
 def mark_as_read(
     request: Request,
     conversation_id: int = Path(..., description="Conversation ID", gt=0),
-    customer: Customer = Depends(get_current_customer_api),
+    customer: CustomerContext = Depends(get_current_customer_api),
     db: Session = Depends(get_db),
 ):
     """Mark conversation as read."""
@@ -394,7 +394,7 @@ async def download_attachment(
     request: Request,
     conversation_id: int = Path(..., description="Conversation ID", gt=0),
     attachment_id: int = Path(..., description="Attachment ID", gt=0),
-    customer: Customer = Depends(get_current_customer_api),
+    customer: CustomerContext = Depends(get_current_customer_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -439,7 +439,7 @@ async def get_attachment_thumbnail(
     request: Request,
     conversation_id: int = Path(..., description="Conversation ID", gt=0),
     attachment_id: int = Path(..., description="Attachment ID", gt=0),
-    customer: Customer = Depends(get_current_customer_api),
+    customer: CustomerContext = Depends(get_current_customer_api),
     db: Session = Depends(get_db),
 ):
     """
@@ -503,7 +503,7 @@ def _get_other_participant_name(conversation, customer_id: int) -> str:
 def _get_sender_name(message) -> str:
     """Get sender name for a message."""
     if message.sender_type == ParticipantType.CUSTOMER:
-        from models.database.customer import Customer
+        from app.modules.customers.models import Customer
 
         customer = (
             Customer.query.filter_by(id=message.sender_id).first()