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/generate.go

@@ -22,9 +22,9 @@ type PRDescription struct {
 
 // GeneratePR generates a structured PR description from commit history and diff.
 // It streams progress via the callback and returns the parsed PR description.
-func GeneratePR(db *sql.DB, repoPath, base, head string, callback StreamCallback) (*PRDescription, error) {
-	// Read LLM config
-	config, err := GetLLMConfig(db)
+func GeneratePR(db *sql.DB, repoPath, base, head string, userID int64, callback StreamCallback) (*PRDescription, error) {
+	// Read LLM config (per-user)
+	config, err := GetLLMConfig(db, userID)
 	if err != nil {
 		return nil, err
 	}

services/llm.go

@@ -17,11 +17,11 @@ type LLMConfig struct {
 	Model    string
 }
 
-// GetLLMConfig reads LLM settings from the database.
-func GetLLMConfig(db *sql.DB) (LLMConfig, error) {
+// GetLLMConfig reads LLM settings from the user_settings table for the given user.
+func GetLLMConfig(db *sql.DB, userID int64) (LLMConfig, error) {
 	config := LLMConfig{}
 
-	rows, err := db.Query(`SELECT key, value FROM settings WHERE key IN ('llm.endpoint', 'llm.api_key', 'llm.model')`)
+	rows, err := db.Query(`SELECT key, value FROM user_settings WHERE user_id = ? AND key IN ('llm.endpoint', 'llm.api_key', 'llm.model')`, userID)
 	if err != nil {
 		return config, fmt.Errorf("read settings: %w", err)
 	}

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
 	}