Add asset proxy feature for resource URLs

Introduces asset proxy configuration and services to enable replacement of osu! resource URLs with custom domains. Updates API endpoints and caching services to process and rewrite resource URLs when asset proxy is enabled. Adds documentation and environment variables for asset proxy setup.

app/router/v2/user.py

@@ -22,11 +22,12 @@ from app.log import logger
 from app.models.score import GameMode
 from app.models.user import BeatmapsetType
 from app.service.user_cache_service import get_user_cache_service
+from app.service.asset_proxy_helper import process_response_assets
 from app.utils import utcnow
 
 from .router import router
 
-from fastapi import BackgroundTasks, HTTPException, Path, Query, Security
+from fastapi import BackgroundTasks, HTTPException, Path, Query, Request, Security
 from pydantic import BaseModel
 from sqlmodel import exists, false, select
 from sqlmodel.sql.expression import col
@@ -47,6 +48,7 @@ class BatchUserResponse(BaseModel):
 @router.get("/users/lookup/", response_model=BatchUserResponse, include_in_schema=False)
 async def get_users(
     session: Database,
+    request: Request,
     background_task: BackgroundTasks,
     user_ids: list[int] = Query(default_factory=list, alias="ids[]", description="要查询的用户 ID 列表"),
     # current_user: User = Security(get_current_user, scopes=["public"]),
@@ -83,7 +85,10 @@ async def get_users(
                     # 异步缓存，不阻塞响应
                     background_task.add_task(cache_service.cache_user, user_resp)
 
-        return BatchUserResponse(users=cached_users)
+        # 处理资源代理
+        response = BatchUserResponse(users=cached_users)
+        processed_response = await process_response_assets(response, request)
+        return processed_response
     else:
         searched_users = (await session.exec(select(User).limit(50))).all()
         users = []
@@ -98,7 +103,10 @@ async def get_users(
                 # 异步缓存
                 background_task.add_task(cache_service.cache_user, user_resp)
 
-        return BatchUserResponse(users=users)
+        # 处理资源代理
+        response = BatchUserResponse(users=users)
+        processed_response = await process_response_assets(response, request)
+        return processed_response
 
 
 @router.get("/users/{user}/recent_activity", tags=["用户"], response_model=list[Event])
@@ -182,6 +190,7 @@ async def get_user_info_ruleset(
 async def get_user_info(
     background_task: BackgroundTasks,
     session: Database,
+    request: Request,
     user_id: str = Path(description="用户 ID 或用户名"),
     # current_user: User = Security(get_current_user, scopes=["public"]),
 ):
@@ -193,7 +202,9 @@ async def get_user_info(
         user_id_int = int(user_id)
         cached_user = await cache_service.get_user_from_cache(user_id_int)
         if cached_user:
-            return cached_user
+            # 处理资源代理
+            processed_user = await process_response_assets(cached_user, request)
+            return processed_user
 
     searched_user = (
         await session.exec(
@@ -214,7 +225,9 @@ async def get_user_info(
     # 异步缓存结果
     background_task.add_task(cache_service.cache_user, user_resp)
 
-    return user_resp
+    # 处理资源代理
+    processed_user = await process_response_assets(user_resp, request)
+    return processed_user
 
 
 @router.get(