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/chat_room/models.py

@@ -79,6 +79,7 @@ class IncidentRoom(Base):
     # Relationships
     members = relationship("RoomMember", back_populates="room", cascade="all, delete-orphan")
     files = relationship("RoomFile", back_populates="room", cascade="all, delete-orphan")
+    reports = relationship("GeneratedReport", back_populates="room", cascade="all, delete-orphan")
 
     # Indexes for common queries
     __table_args__ = (

app/modules/chat_room/router.py

@@ -193,7 +193,7 @@ async def permanent_delete_room(
         "type": "system",
         "event": "room_deleted",
         "room_id": room_id,
-        "timestamp": datetime.utcnow().isoformat()
+        "timestamp": datetime.utcnow().isoformat() + "Z"
     })
 
     success, error = room_service.permanent_delete_room(db, room_id)
@@ -246,7 +246,7 @@ async def join_room(
             detail={
                 "message": "Already a member of this room",
                 "current_role": existing.role.value,
-                "added_at": existing.added_at.isoformat()
+                "added_at": existing.added_at.isoformat() + "Z"
             }
         )
 
@@ -505,12 +505,12 @@ async def add_lot(
         raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Room not found")
 
     # Get current lots or initialize empty list
-    current_lots = room.lots or []
+    current_lots = list(room.lots or [])  # Create a new list to ensure change detection
 
     # Prevent duplicates
     if request.lot not in current_lots:
         current_lots.append(request.lot)
-        room.lots = current_lots
+        room.lots = current_lots  # Assign new list triggers SQLAlchemy change detection
         room.last_updated_at = datetime.utcnow()
         db.commit()
         db.refresh(room)
@@ -532,11 +532,11 @@ async def remove_lot(
     if not room:
         raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Room not found")
 
-    current_lots = room.lots or []
+    current_lots = list(room.lots or [])  # Create a new list to ensure change detection
 
     if lot in current_lots:
         current_lots.remove(lot)
-        room.lots = current_lots
+        room.lots = current_lots  # Assign new list triggers SQLAlchemy change detection
         room.last_updated_at = datetime.utcnow()
         db.commit()
         db.refresh(room)

app/modules/chat_room/schemas.py

@@ -2,7 +2,7 @@
 
 Request and response models for API endpoints
 """
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, Field, ConfigDict, field_serializer
 from typing import Optional, List
 from datetime import datetime
 from enum import Enum
@@ -98,8 +98,14 @@ class MemberResponse(BaseModel):
     added_at: datetime
     removed_at: Optional[datetime] = None
 
-    class Config:
-        from_attributes = True
+    model_config = ConfigDict(from_attributes=True)
+
+    @field_serializer("added_at", "removed_at")
+    def serialize_datetime(self, dt: Optional[datetime]) -> Optional[str]:
+        """Serialize datetime with 'Z' suffix to indicate UTC"""
+        if dt is None:
+            return None
+        return dt.isoformat() + "Z"
 
 
 class RoomResponse(BaseModel):
@@ -127,8 +133,17 @@ class RoomResponse(BaseModel):
     is_member: bool = False
     is_admin_view: bool = False
 
-    class Config:
-        from_attributes = True
+    model_config = ConfigDict(from_attributes=True)
+
+    @field_serializer(
+        "created_at", "resolved_at", "archived_at",
+        "last_activity_at", "last_updated_at", "ownership_transferred_at"
+    )
+    def serialize_datetime(self, dt: Optional[datetime]) -> Optional[str]:
+        """Serialize datetime with 'Z' suffix to indicate UTC"""
+        if dt is None:
+            return None
+        return dt.isoformat() + "Z"
 
 
 class RoomListResponse(BaseModel):

app/modules/chat_room/services/room_service.py

@@ -467,7 +467,11 @@ class RoomService:
                             f"Failed to delete report file: {report.docx_storage_path}"
                         )
 
-            # Step 3: Delete room from database (CASCADE handles related tables)
+            # Step 3: Delete reports from database (before room delete due to relationship handling)
+            for report in reports:
+                db.delete(report)
+
+            # Step 4: Delete room from database (CASCADE handles other related tables)
             db.delete(room)
             db.commit()