fix: add avatar photo upload endpoint to digital-avatar-app backend

- Add POST /api/avatar/{id}/photo endpoint
- Save uploaded photos to UPLOAD_DIR/{avatar_id}/
- Update avatar.photo_url in database
- Import UPLOAD_DIR from knowledge router

digital-avatar-app/backend/routers/avatars.py

@@ -1,7 +1,11 @@
-from fastapi import APIRouter, Depends, Body, Header
+from fastapi import APIRouter, Depends, Body, Header, UploadFile, File
 from sqlalchemy.orm import Session
+import os
+import uuid
+import mimetypes
 
 from database import get_db
+from routers.knowledge import UPLOAD_DIR
 from models import Avatar, KnowledgeDoc, KnowledgeChunk, QAPair, Authorization, User
 from responses import ok, fail
 
@@ -93,3 +97,41 @@ def delete_avatar(avatar_id: str, db: Session = Depends(get_db)):
     db.delete(a)
     db.commit()
     return ok({"success": True})
+
+
+@router.post("/avatar/{avatar_id}/photo")
+async def upload_avatar_photo(
+    avatar_id: str,
+    file: UploadFile = File(...),
+    db: Session = Depends(get_db),
+):
+    """上传数字分身头像"""
+    a = db.query(Avatar).filter(Avatar.id == avatar_id).first()
+    if not a:
+        return fail("分身不存在", 404)
+
+    # 验证文件类型
+    if not file.content_type or not file.content_type.startswith("image/"):
+        return fail("仅支持图片文件", 400)
+
+    file_bytes = await file.read()
+    if len(file_bytes) > 5 * 1024 * 1024:
+        return fail("头像文件不能超过5MB", 400)
+
+    # 保存到 uploads 目录
+    ext = mimetypes.guess_extension(file.content_type) or ".jpg"
+    filename = f"avatar-{uuid.uuid4().hex}{ext}"
+    avatar_dir = os.path.join(UPLOAD_DIR, avatar_id)
+    os.makedirs(avatar_dir, exist_ok=True)
+    file_path = os.path.join(avatar_dir, filename)
+
+    with open(file_path, "wb") as f:
+        f.write(file_bytes)
+
+    # 更新数据库
+    photo_url = f"/api/files/{avatar_id}/{filename}"
+    a.photo_url = photo_url
+    db.commit()
+    db.refresh(a)
+
+    return ok(a.to_dict())