feat(user): implement user restrictions

## APIs Restricted for Restricted Users

A restricted user is blocked from performing the following actions, and will typically receive a `403 Forbidden` error:

*   **Chat & Notifications:**
    *   Sending any chat messages (public or private).
    *   Joining or leaving chat channels.
    *   Creating new PM channels.
*   **User Profile & Content:**
    *   Uploading a new avatar.
    *   Uploading a new profile cover image.
    *   Changing their username.
    *   Updating their userpage content.
*   **Scores & Gameplay:**
    *   Submitting scores in multiplayer rooms.
    *   Deleting their own scores (to prevent hiding evidence of cheating).
*   **Beatmaps:**
    *   Rating beatmaps.
    *   Taging beatmaps.
*   **Relationship:**
    *   Adding friends or blocking users.
    *   Removing friends or unblocking users.
*   **Teams:**
    *   Creating, updating, or deleting a team.
    *   Requesting to join a team.
    *   Handling join requests for a team they manage.
    *   Kicking a member from a team they manage.
*   **Multiplayer:**
    *   Creating or deleting multiplayer rooms.
    *   Joining or leaving multiplayer rooms.

## What is Invisible to Normal Users

*   **Leaderboards:**
    *   Beatmap leaderboards.
    *   Multiplayer (playlist) room leaderboards.
*   **User Search/Lists:**
    *   Restricted users will not appear in the results of the `/api/v2/users` endpoint.
    *   They will not appear in the list of a team's members.
*   **Relationship:**
    *   They will not appear in a user's friend list (`/friends`).
*   **Profile & History:**
    *   Attempting to view a restricted user's profile, events, kudosu history, or score history will result in a `404 Not Found` error, effectively making their profile invisible (unless the user viewing the profile is the restricted user themselves).
*   **Chat:**
    *   Normal users cannot start a new PM with a restricted user (they will get a `404 Not Found` error).
*   **Ranking:**
    *   Restricted users are excluded from any rankings.

### How to Restrict a User

Insert into `user_account_history` with `type=restriction`.

```sql
-- length is in seconds
INSERT INTO user_account_history (`description`, `length`, `permanent`, `timestamp`, `type`, `user_id`) VALUE ('some description', 86400, 0, '2025-10-05 01:00:00', 'RESTRICTION', 1);
```

---

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

app/tasks/cache.py

@@ -6,7 +6,8 @@ from typing import Final
 
 from app.config import settings
 from app.database.score import Score
-from app.dependencies.database import get_redis
+from app.database.user import User
+from app.dependencies.database import get_redis, with_db
 from app.dependencies.fetcher import get_fetcher
 from app.dependencies.scheduler import get_scheduler
 from app.log import logger
@@ -107,9 +108,6 @@ async def schedule_user_cache_warmup_task() -> None:
 
         redis = get_redis()
         cache_service = get_user_cache_service(redis)
-
-        from app.dependencies.database import with_db
-
         async with with_db() as session:
             from app.database.statistics import UserStatistics
             from app.models.score import GameMode
@@ -119,7 +117,10 @@ async def schedule_user_cache_warmup_task() -> None:
                     top_users = (
                         await session.exec(
                             select(UserStatistics.user_id)
-                            .where(UserStatistics.mode == mode)
+                            .where(
+                                UserStatistics.mode == mode,
+                                ~User.is_restricted_query(col(UserStatistics.user_id)),
+                            )
                             .order_by(col(UserStatistics.pp).desc())
                             .limit(100)
                         )