fix(upload): configure chat attachment size limit (#2439)

src/upload_handler.py

@@ -12,6 +12,10 @@ import threading
 from datetime import datetime, timedelta
 from typing import Dict, Any, Optional
 from fastapi import HTTPException, UploadFile
+
+from src.upload_limits import format_byte_limit, get_chat_upload_max_bytes
+
+
 def secure_filename(filename: str) -> str:
     """Sanitize a filename (replaces werkzeug.utils.secure_filename)."""
     import unicodedata
@@ -73,7 +77,7 @@ class UploadHandler:
     def __init__(self, base_dir: str, upload_dir: str):
         self.base_dir = base_dir
         self.upload_dir = upload_dir
-        self.max_upload_size = 10 * 1024 * 1024  # 10MB
+        self.max_upload_size = get_chat_upload_max_bytes()
         self.max_concurrent_uploads = 3
         self.cleanup_days = 30
         # Per-IP per-minute cap. save_upload() counts EACH file, and the chat
@@ -518,7 +522,7 @@ class UploadHandler:
         if file_size > self.max_upload_size:
             raise HTTPException(
                 status_code=400,
-                detail=f"File size exceeds {self.max_upload_size/1024/1024}MB limit"
+                detail=f"File size exceeds {format_byte_limit(self.max_upload_size)} limit"
             )
         
         # Get original filename and sanitize it