refactor: 统一日志管理 + 数据库索引优化

- db/schema.py: 添加 4 个复合索引优化查询性能
  - idx_user_schedules_user_enabled
  - idx_schedule_execution_logs_schedule_id/user_id/status
- db/users.py: print → logger，密码升级日志改为记录 user_id
- crypto_utils.py: print → logger
- password_utils.py: print → logger

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

db/schema.py

@@ -260,6 +260,11 @@ def ensure_schema(conn) -> None:
     cursor.execute("CREATE INDEX IF NOT EXISTS idx_user_schedules_user_id ON user_schedules(user_id)")
     cursor.execute("CREATE INDEX IF NOT EXISTS idx_user_schedules_enabled ON user_schedules(enabled)")
     cursor.execute("CREATE INDEX IF NOT EXISTS idx_user_schedules_next_run ON user_schedules(next_run_at)")
+    # 复合索引优化
+    cursor.execute("CREATE INDEX IF NOT EXISTS idx_user_schedules_user_enabled ON user_schedules(user_id, enabled)")
+    cursor.execute("CREATE INDEX IF NOT EXISTS idx_schedule_execution_logs_schedule_id ON schedule_execution_logs(schedule_id)")
+    cursor.execute("CREATE INDEX IF NOT EXISTS idx_schedule_execution_logs_user_id ON schedule_execution_logs(user_id)")
+    cursor.execute("CREATE INDEX IF NOT EXISTS idx_schedule_execution_logs_status ON schedule_execution_logs(status)")
 
     # 初始化VIP配置（幂等）
     try: