fix: Add file upload endpoint and fix frontend upload path

api/routers/quality.py

@@ -15,10 +15,13 @@ Provides endpoints for:
 - Quality gate evaluation
 """
 
-from fastapi import APIRouter, HTTPException, Path, Body
+from fastapi import APIRouter, HTTPException, Path, Body, File, UploadFile, Query
 from pydantic import BaseModel, Field
 from typing import List, Optional
 from loguru import logger
+import os
+import shutil
+from datetime import datetime
 
 router = APIRouter(prefix="/quality", tags=["Quality"])
 
@@ -255,6 +258,47 @@ async def analyze_character_image(
         prompt_description=result.to_prompt_description()
     )
 
+
+@router.post("/upload")
+async def upload_file(
+    file: UploadFile = File(...),
+    storyboard_id: str = Query(..., description="Storyboard ID"),
+    type: str = Query("character", description="File type (character, reference)")
+):
+    """
+    Upload a file for character reference or other purposes.
+    
+    Returns the saved file path that can be used for analysis.
+    """
+    try:
+        # Create output directory
+        output_dir = f"output/{storyboard_id}"
+        os.makedirs(output_dir, exist_ok=True)
+        
+        # Generate filename with timestamp
+        timestamp = datetime.now().strftime("%Y%m%d_%H%M%S_%f")
+        ext = os.path.splitext(file.filename)[1] or ".png"
+        filename = f"{type}_{timestamp}{ext}"
+        file_path = os.path.join(output_dir, filename)
+        
+        # Save file
+        with open(file_path, "wb") as buffer:
+            content = await file.read()
+            buffer.write(content)
+        
+        logger.info(f"Uploaded file to: {file_path}")
+        
+        return {
+            "success": True,
+            "path": file_path,
+            "file_path": file_path,
+            "filename": filename
+        }
+        
+    except Exception as e:
+        logger.error(f"Failed to upload file: {e}")
+        raise HTTPException(status_code=500, detail=str(e))
+
 # ============================================================
 # Content Filter Endpoints
 # ============================================================