refactor: introduce Wire dependency injection and interface-based architecture

- Add Google Wire for compile-time dependency injection
- Replace concrete service types with interfaces across handlers
- Remove global state (DB, cache) in favor of constructor injection
- Split monolithic files into focused modules:
  - config: separate files for each config domain
  - dto: converters split by domain (user, post, message, group)
  - cache: separate metrics.go and redis_cache.go
- Introduce unified apperrors package with string-based error codes
- Add transaction support with context-aware repository methods
- Upgrade golang.org/x/crypto from 0.17.0 to 0.26.0

internal/config/jwt.go

@@ -0,0 +1,10 @@
+package config
+
+import "time"
+
+// JWTConfig JWT 配置
+type JWTConfig struct {
+	Secret             string        `mapstructure:"secret"`
+	AccessTokenExpire  time.Duration `mapstructure:"access_token_expire"`
+	RefreshTokenExpire time.Duration `mapstructure:"refresh_token_expire"`
+}