GitLab

新增 GetByIDLite 并在网关与 Gemini 选择流程复用上下文 group，避免 COUNT 触发
更新 API key 中间件注入 group 上下文，减少重复查库
补充 gateway/gemini 中间件与仓库层回归测试

测试: make test

- Add claude_code_only field to restrict groups to Claude Code clients only
- Add fallback_group_id for non-Claude Code requests to use alternate group
- Implement ClaudeCodeValidator for User-Agent detection
- Add group-level session binding isolation (groupID in Redis key)
- Prevent cross-group sticky session pollution
- Update frontend with Claude Code restriction controls

- SA1029: 创建 ctxkey 包定义类型安全的 context key
- ST1005: 错误字符串首字母改小写
- errcheck: 显式忽略 bytes.Buffer.Write 返回值
- 修复单元测试中 GatewayService 缺少 cfg 字段的问题