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/report_generation/prompts.py

@@ -4,7 +4,18 @@ Contains the prompt construction logic for building the user query
 sent to DIFY Chat API.
 """
 from typing import List, Dict, Any
-from datetime import datetime
+from datetime import datetime, timezone, timedelta
+
+# Taiwan timezone (GMT+8)
+TZ_GMT8 = timezone(timedelta(hours=8))
+
+
+def _to_gmt8(dt: datetime) -> datetime:
+    """Convert datetime to GMT+8 timezone"""
+    if dt.tzinfo is None:
+        # Assume UTC if no timezone
+        dt = dt.replace(tzinfo=timezone.utc)
+    return dt.astimezone(TZ_GMT8)
 
 
 INCIDENT_TYPE_MAP = {
@@ -81,11 +92,11 @@ def _format_room_info(room_data: Dict[str, Any]) -> str:
 
     created_at = room_data.get("created_at")
     if isinstance(created_at, datetime):
-        created_at = created_at.strftime("%Y-%m-%d %H:%M")
+        created_at = _to_gmt8(created_at).strftime("%Y-%m-%d %H:%M")
 
     resolved_at = room_data.get("resolved_at")
     if isinstance(resolved_at, datetime):
-        resolved_at = resolved_at.strftime("%Y-%m-%d %H:%M")
+        resolved_at = _to_gmt8(resolved_at).strftime("%Y-%m-%d %H:%M")
     elif resolved_at is None:
         resolved_at = "尚未解決"
 
@@ -145,7 +156,7 @@ def _format_messages(messages: List[Dict[str, Any]]) -> str:
 
         created_at = msg.get("created_at")
         if isinstance(created_at, datetime):
-            time_str = created_at.strftime("%Y-%m-%d %H:%M")
+            time_str = _to_gmt8(created_at).strftime("%Y-%m-%d %H:%M")
         else:
             time_str = str(created_at) if created_at else "未知時間"
 
@@ -164,26 +175,58 @@ def _format_messages(messages: List[Dict[str, Any]]) -> str:
 
 
 def _format_files(files: List[Dict[str, Any]]) -> str:
-    """Format file attachments section"""
+    """Format file attachments section with context
+
+    Each file now includes:
+    - caption: User-provided description when uploading
+    - context_before: The message sent before this file
+    - context_after: The message sent after this file
+
+    This helps AI understand the context of each attachment.
+    """
     lines = ["## 附件清單"]
+    lines.append("每個附件包含上傳時的說明文字以及上下文訊息，幫助理解該附件的用途。")
+    lines.append("")
 
     if not files:
         lines.append("無附件")
         return "\n".join(lines)
 
-    for f in files:
+    for i, f in enumerate(files, 1):
         filename = f.get("filename", "未命名檔案")
         file_type = f.get("file_type", "file")
         uploader = f.get("uploader_name") or f.get("uploaded_by", "未知")
+        caption = f.get("caption")  # User-provided description
+        context_before = f.get("context_before")
+        context_after = f.get("context_after")
 
         uploaded_at = f.get("uploaded_at")
         if isinstance(uploaded_at, datetime):
-            time_str = uploaded_at.strftime("%Y-%m-%d %H:%M")
+            time_str = _to_gmt8(uploaded_at).strftime("%Y-%m-%d %H:%M")
         else:
             time_str = str(uploaded_at) if uploaded_at else ""
 
         type_label = "圖片" if file_type == "image" else "檔案"
-        lines.append(f"- [{type_label}] {filename} (由 {uploader} 於 {time_str} 上傳)")
+
+        # Basic file info
+        lines.append(f"### 附件 {i}: {filename}")
+        lines.append(f"- 類型: {type_label}")
+        lines.append(f"- 上傳者: {uploader}")
+        lines.append(f"- 上傳時間: {time_str}")
+
+        # Caption/description if provided
+        if caption:
+            lines.append(f"- 說明: {caption}")
+
+        # Context messages to help AI understand when/why file was uploaded
+        if context_before or context_after:
+            lines.append("- 上下文:")
+            if context_before:
+                lines.append(f"  - 前一則訊息: [{context_before['sender']}]: {context_before['content']}")
+            if context_after:
+                lines.append(f"  - 後一則訊息: [{context_after['sender']}]: {context_after['content']}")
+
+        lines.append("")  # Blank line between files
 
     return "\n".join(lines)