refactor: move business logic to service layer for architecture compliance

- images.py: delegate file validation (size, type, extension) to image_service
- platform_health.py: extract all database queries to platform_health_service
- Fixes 13 architecture validation errors (API-002, API-003)

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

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

app/services/image_service.py

@@ -12,21 +12,26 @@ Provides:
 import hashlib
 import logging
 import os
-import shutil
 from datetime import datetime
 from io import BytesIO
 from pathlib import Path
 
 from PIL import Image
 
+from app.exceptions import ValidationException
+
 logger = logging.getLogger(__name__)
 
+# Maximum upload size (10MB)
+MAX_UPLOAD_SIZE = 10 * 1024 * 1024
+
 
 class ImageService:
     """Service for image upload and management."""
 
     # Supported image formats
     ALLOWED_EXTENSIONS = {"jpg", "jpeg", "png", "gif", "webp"}
+    ALLOWED_CONTENT_TYPES = {"image/jpeg", "image/png", "image/gif", "image/webp"}
 
     # Size variants to generate
     SIZES = {
@@ -57,6 +62,7 @@ class ImageService:
         filename: str,
         vendor_id: int,
         product_id: int | None = None,
+        content_type: str | None = None,
     ) -> dict:
         """Upload and process a product image.
 
@@ -65,14 +71,30 @@ class ImageService:
             filename: Original filename
             vendor_id: Vendor ID for path generation
             product_id: Optional product ID
+            content_type: MIME type of the uploaded file
 
         Returns:
             Dict with image info and URLs
+
+        Raises:
+            ValidationException: If file is too large or invalid type
         """
+        # Validate file size
+        if len(file_content) > MAX_UPLOAD_SIZE:
+            raise ValidationException(
+                f"File too large. Maximum size: {MAX_UPLOAD_SIZE // (1024*1024)}MB"
+            )
+
+        # Validate content type
+        if not content_type or not content_type.startswith("image/"):
+            raise ValidationException("Invalid file type. Only images are allowed.")
+
         # Validate file extension
         ext = self._get_extension(filename)
         if ext not in self.ALLOWED_EXTENSIONS:
-            raise ValueError(f"Invalid file type: {ext}. Allowed: {self.ALLOWED_EXTENSIONS}")
+            raise ValidationException(
+                f"Invalid file type: {ext}. Allowed: {', '.join(self.ALLOWED_EXTENSIONS)}"
+            )
 
         # Generate unique hash for this image
         image_hash = self._generate_hash(vendor_id, product_id, filename)