feat: Improve file display, timezone handling, and LOT management

Changes:
- Fix datetime serialization with UTC 'Z' suffix for correct timezone display
- Add PDF upload support with extension fallback for MIME detection
- Fix LOT add/remove by creating new list for SQLAlchemy JSON change detection
- Add file message components (FileMessage, ImageLightbox, UploadPreview)
- Add multi-file upload support with progress tracking
- Link uploaded files to chat messages via message_id
- Include file attachments in AI report generation
- Update specs for file-storage, realtime-messaging, and ai-report-generation

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

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

app/modules/file_storage/services/file_service.py

@@ -69,11 +69,38 @@ class FileService:
                 detail="File storage service temporarily unavailable"
             )
 
-        # Create database record
+        # Create database record and associated message
         try:
+            # Generate presigned download URL
+            download_url = minio_service.generate_presigned_url(
+                bucket=settings.MINIO_BUCKET,
+                object_path=object_path,
+                expiry_seconds=3600
+            )
+
+            # For images, the download URL also serves as thumbnail (CSS resized on frontend)
+            thumbnail_url = download_url if file_type == "image" else None
+
+            # Create the associated chat message first
+            message = FileService.create_file_reference_message(
+                db=db,
+                room_id=room_id,
+                sender_id=uploader_id,
+                file_id=file_id,
+                filename=file.filename,
+                file_type=file_type,
+                mime_type=mime_type,
+                file_size=file_size,
+                file_url=download_url,
+                thumbnail_url=thumbnail_url,
+                description=description
+            )
+
+            # Create file record with message_id reference
             room_file = RoomFile(
                 file_id=file_id,
                 room_id=room_id,
+                message_id=message.message_id,
                 uploader_id=uploader_id,
                 filename=file.filename,
                 file_type=file_type,
@@ -88,20 +115,15 @@ class FileService:
             db.commit()
             db.refresh(room_file)
 
-            # Generate presigned download URL
-            download_url = minio_service.generate_presigned_url(
-                bucket=settings.MINIO_BUCKET,
-                object_path=object_path,
-                expiry_seconds=3600
-            )
-
             return FileUploadResponse(
                 file_id=file_id,
+                message_id=message.message_id,
                 filename=file.filename,
                 file_type=file_type,
                 file_size=file_size,
                 mime_type=mime_type,
                 download_url=download_url,
+                thumbnail_url=thumbnail_url,
                 uploaded_at=room_file.uploaded_at,
                 uploader_id=uploader_id
             )
@@ -160,12 +182,17 @@ class FileService:
         file_id: str,
         user_id: str,
         is_room_owner: bool = False
-    ) -> Optional[RoomFile]:
-        """Soft delete file"""
+    ) -> tuple[Optional[RoomFile], Optional[str]]:
+        """
+        Soft delete file and its associated message.
+
+        Returns:
+            Tuple of (deleted_file, deleted_message_id) or (None, None) if not found
+        """
         file = db.query(RoomFile).filter(RoomFile.file_id == file_id).first()
 
         if not file:
-            return None
+            return None, None
 
         # Check permissions
         if not is_room_owner and file.uploader_id != user_id:
@@ -174,12 +201,21 @@ class FileService:
                 detail="Only file uploader or room owner can delete files"
             )
 
-        # Soft delete
+        deleted_message_id = None
+
+        # Soft delete the associated message if it exists
+        if file.message_id:
+            message = db.query(Message).filter(Message.message_id == file.message_id).first()
+            if message and message.deleted_at is None:
+                message.deleted_at = datetime.utcnow()
+                deleted_message_id = message.message_id
+
+        # Soft delete the file
         file.deleted_at = datetime.utcnow()
         db.commit()
         db.refresh(file)
 
-        return file
+        return file, deleted_message_id
 
     @staticmethod
     def check_room_membership(db: Session, room_id: str, user_id: str) -> Optional[RoomMember]:
@@ -205,7 +241,10 @@ class FileService:
         file_id: str,
         filename: str,
         file_type: str,
+        mime_type: str,
+        file_size: int,
         file_url: str,
+        thumbnail_url: Optional[str] = None,
         description: Optional[str] = None
     ) -> Message:
         """
@@ -218,7 +257,10 @@ class FileService:
             file_id: File ID in room_files table
             filename: Original filename
             file_type: Type of file (image, document, log)
+            mime_type: MIME type of the file
+            file_size: File size in bytes
             file_url: Presigned download URL
+            thumbnail_url: Presigned thumbnail URL for images
             description: Optional description for the file
 
         Returns:
@@ -237,9 +279,15 @@ class FileService:
             "file_id": file_id,
             "file_url": file_url,
             "filename": filename,
-            "file_type": file_type
+            "file_type": file_type,
+            "mime_type": mime_type,
+            "file_size": file_size
         }
 
+        # Add thumbnail URL for images
+        if thumbnail_url:
+            metadata["thumbnail_url"] = thumbnail_url
+
         # Use MessageService to create the message
         return MessageService.create_message(
             db=db,