feat: 添加用户注册登录功能，实现数据和配置的用户隔离

- 新增 users 和 user_settings 表，repositories/analyses/review_notes 添加 user_id 列
- 实现基于邮箱+密码的注册登录，密码使用 bcrypt 哈希
- 使用 gin-contrib/sessions cookie-based session 管理
- 所有仓库、分析记录、review notes 按用户隔离
- 用户设置（LLM 配置、review 参数、缓存配置）独立存储
- 新增登录/注册页面，导航栏显示用户邮箱和退出按钮
- 前端 fetch 请求统一添加 credentials: 'same-origin'
- 支持 SESSION_SECRET 环境变量配置会话密钥

services/review.go

@@ -58,9 +58,9 @@ func countDiffLines(patch string) int {
 // GenerateReview performs AI code review on diff files with Top-N strategy.
 // It streams events (file_start, suggestion, file_end, summary, done) via callback
 // and returns the complete ReviewResult for persistence.
-func GenerateReview(db *sql.DB, repoPath, base, head string, topN, concurrency int, callback StreamCallback) (*ReviewResult, error) {
-	// Read LLM config
-	config, err := GetLLMConfig(db)
+func GenerateReview(db *sql.DB, repoPath, base, head string, topN, concurrency int, userID int64, callback StreamCallback) (*ReviewResult, error) {
+	// Read LLM config (per-user)
+	config, err := GetLLMConfig(db, userID)
 	if err != nil {
 		return nil, err
 	}