merge: Phase 1 image system implementation complete

- Database: Added photo_path, photo_thumbnail_path, photo_upload_date fields
- Services: ImageStorage (file ops) + ImageProcessor (image processing pipeline)
- API: POST/PUT /api/items/{id}/photo upload endpoints with validation
- API: GET /api/items/{id} returns photo URLs
- Static: FastAPI StaticFiles mount for /images/ directory
- Tests: 127+ comprehensive tests across all components
- Security: Fixed race conditions, path traversal, crop validation
- Ready for Phase 2 (frontend UI)

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

backend/schemas/items.py

@@ -3,6 +3,14 @@ from typing import Optional
 from datetime import datetime
 
 
+# --- Photo Response ---
+class PhotoResponse(BaseModel):
+    """Photo metadata for item responses."""
+    thumbnail_url: str
+    full_url: str
+    uploaded_at: datetime
+
+
 # --- Categories ---
 class CategoryBase(BaseModel):
     name: str
@@ -66,6 +74,10 @@ class ItemCreate(ItemBase):
 
 class Item(ItemBase):
     id: int
+    photo_path: Optional[str] = None
+    photo_thumbnail_path: Optional[str] = None
+    photo_upload_date: Optional[datetime] = None
+    photo: Optional[PhotoResponse] = None
 
     class Config:
         from_attributes = True