fix(media): Add MPO format support for iPhone portrait photos

iPhones use MPO (Multi-Picture Object) format for depth/portrait photos.
This format contains multiple JPEG images (main + depth map). Pillow
opens these as MPO format which wasn't in our allowed types.

Added automatic MPO to JPEG conversion by extracting the primary image.

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

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

starpunk/media.py

@@ -160,6 +160,18 @@ def validate_image(file_data: bytes, filename: str) -> Tuple[bytes, str, int, in
         file_data = output.getvalue()
         img = Image.open(io.BytesIO(file_data))
 
+    # MPO (Multi-Picture Object) conversion (v1.4.2)
+    # MPO is used by iPhones for depth/portrait photos - extract primary image as JPEG
+    if img.format == 'MPO':
+        output = io.BytesIO()
+        # Convert to RGB if needed
+        if img.mode in ('RGBA', 'P'):
+            img = img.convert('RGB')
+        img.save(output, format='JPEG', quality=95)
+        output.seek(0)
+        file_data = output.getvalue()
+        img = Image.open(io.BytesIO(file_data))
+
     # Check format is allowed
     if img.format:
         format_lower = img.format.lower()