style(rmi-backend): complete lint cleanup — 1175→0 ruff errors

- Fix 71 invalid-syntax files (class-body newline-broken assignments)
- Add from/None chain to 307 B904 raise-without-from sites
- Add B008 ignore to ruff.toml (already in pyproject.toml)
- Noqa F401 on __init__.py re-exports (137 sites)
- Noqa E402 on deferred imports (63 sites)
- Bulk-add stdlib/FastAPI/project imports for F821 (127 sites)
- Replace ×→x, –→-, …→... in docstrings (4093 chars)
- Manual refactor of 5 SIM103/SIM116 patterns

Tests: 791 passed (66 deselected due to pre-existing Redis issues in test_rag.py)
Co-authored-by: opencode <opencode@rugmunch.io>

app/routers/admin_users_api.py

@@ -16,6 +16,7 @@ All endpoints require ADMIN or SUPERADMIN role.
 
 import json
 import logging
+import secrets
 from datetime import datetime, timedelta
 from enum import StrEnum
 from typing import Any
@@ -23,6 +24,8 @@ from typing import Any
 from fastapi import APIRouter, HTTPException, Query, Request
 from pydantic import BaseModel, Field
 
+from app.core.redis import get_redis
+
 logger = logging.getLogger("rmi_admin_users")
 router = APIRouter(tags=["admin-users"])