feat(backend): Go 服务骨架（配置、日志、数据库、中间件、Wire）

- config: Viper YAML 配置 + 环境变量覆盖
- logs: zap 结构化日志 + trace_id 链路追踪 + 敏感信息脱敏
- db: PostgreSQL (GORM) + Redis (go-redis) 连接管理
- middleware: Trace/Logger/CORS/Recovery 四层中间件
- provider: Wire 编译时依赖注入
- main.go: 优雅启动/关闭 HTTP 服务

Made-with: Cursor

backend/go-service/app/provider/wire_gen.go

@@ -0,0 +1,30 @@
+// Code generated by Wire. DO NOT EDIT.
+
+//go:generate go run -mod=mod github.com/google/wire/cmd/wire
+//go:build !wireinject
+// +build !wireinject
+
+package provider
+
+import (
+	"github.com/echochat/backend/config"
+	"github.com/echochat/backend/pkg/db"
+)
+
+// Injectors from wire.go:
+
+// InitializeApp 初始化整个应用（Wire 自动生成实现）
+func InitializeApp(cfg *config.Config) (*App, error) {
+	databaseConfig := provideDBConfig(cfg)
+	gormDB, err := db.NewPostgres(databaseConfig)
+	if err != nil {
+		return nil, err
+	}
+	redisConfig := provideRedisConfig(cfg)
+	client, err := db.NewRedis(redisConfig)
+	if err != nil {
+		return nil, err
+	}
+	app := NewApp(cfg, gormDB, client)
+	return app, nil
+}