refactor: improve system stability, performance, and code structure

This commit introduces several architectural improvements and optimizations across the codebase:

- **Performance & Reliability**:
  - Implemented Redis pipelining in `ConversationCache.CacheMessage` to reduce network round-trips.
  - Added a circuit breaker to the JPush client to prevent cascading failures.
  - Introduced batch deletion and batch member addition capabilities in repositories.
  - Added message idempotency support using `client_msg_id` and a Redis-based cache.
  - Optimized WebSocket handling with connection limits (total and per-user) and improved error logging.

- **Code Refactoring**:
  - Refactored `Router` to use a `RouterDeps` struct, simplifying the constructor and improving maintainability.
  - Unified model ID generation logic using new `id_helper.go` (supporting UUID and Snowflake).
  - Standardized JSON serialization/deserialization in models using `json_helper.go`.
  - Refactored DTO conversion logic, specifically for `UserResponse` (using functional options) and `Report` responses.
  - Removed redundant/deprecated DTOs like `PostDetailResponse` and `TradeItemDetailResponse`.

- **Cache Improvements**:
  - Enhanced `LayeredCache` with `SetRaw` to avoid double-encoding when promoting values from Redis to local cache.
  - Added `DeleteBatch` support to the cache interface.

- **Other Changes**:
  - Cleaned up `config.go` by removing redundant default values and explicit environment variable overrides.
  - Improved WebSocket registration flow to handle connection limits gracefully.

internal/pkg/circuitbreaker/circuitbreaker.go

@@ -0,0 +1,136 @@
+package circuitbreaker
+
+import (
+	"sync"
+	"time"
+
+	"go.uber.org/zap"
+)
+
+type State int
+
+const (
+	StateClosed   State = iota
+	StateOpen
+	StateHalfOpen
+)
+
+type Config struct {
+	FailureThreshold int           // 连续失败次数阈值，超过则开启熔断
+	SuccessThreshold int           // 半开状态下连续成功次数，恢复到关闭
+	Timeout          time.Duration // 熔断开启后等待多久进入半开
+	Name             string       // 熔断器名称，用于日志
+}
+
+func DefaultConfig(name string) Config {
+	return Config{
+		FailureThreshold: 5,
+		SuccessThreshold: 3,
+		Timeout:          30 * time.Second,
+		Name:             name,
+	}
+}
+
+type Breaker struct {
+	cfg    Config
+	mu     sync.Mutex
+	state  State
+	fails  int
+	wins   int
+	openAt time.Time
+}
+
+func New(cfg Config) *Breaker {
+	return &Breaker{cfg: cfg}
+}
+
+func (b *Breaker) Allow() bool {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	switch b.state {
+	case StateClosed:
+		return true
+	case StateOpen:
+		if time.Since(b.openAt) > b.cfg.Timeout {
+			b.state = StateHalfOpen
+			b.wins = 0
+			return true
+		}
+		return false
+	case StateHalfOpen:
+		return true
+	default:
+		return true
+	}
+}
+
+func (b *Breaker) RecordSuccess() {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	b.fails = 0
+	if b.state == StateHalfOpen {
+		b.wins++
+		if b.wins >= b.cfg.SuccessThreshold {
+			b.state = StateClosed
+			b.wins = 0
+			zap.L().Info("circuit breaker closed",
+				zap.String("breaker", b.cfg.Name),
+			)
+		}
+	}
+}
+
+func (b *Breaker) RecordFailure() {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	b.fails++
+	if b.state == StateHalfOpen {
+		b.state = StateOpen
+		b.openAt = time.Now()
+		b.wins = 0
+		zap.L().Warn("circuit breaker re-opened from half-open",
+			zap.String("breaker", b.cfg.Name),
+		)
+		return
+	}
+	if b.fails >= b.cfg.FailureThreshold {
+		b.state = StateOpen
+		b.openAt = time.Now()
+		zap.L().Warn("circuit breaker opened",
+			zap.String("breaker", b.cfg.Name),
+			zap.Int("consecutive_failures", b.fails),
+		)
+	}
+}
+
+func (b *Breaker) State() State {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	return b.state
+}
+
+func (b *Breaker) Execute(fn func() error) error {
+	if !b.Allow() {
+		zap.L().Debug("circuit breaker rejected request",
+			zap.String("breaker", b.cfg.Name),
+		)
+		return &OpenError{Name: b.cfg.Name}
+	}
+	if err := fn(); err != nil {
+		b.RecordFailure()
+		return err
+	}
+	b.RecordSuccess()
+	return nil
+}
+
+type OpenError struct {
+	Name string
+}
+
+func (e *OpenError) Error() string {
+	return "circuit breaker '" + e.Name + "' is open"
+}