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/cache/lru.go

@@ -87,6 +87,39 @@ func (l *LRU) set(key string, value any, ttl time.Duration) {
 	}
 }
 
+// SetRaw stores raw bytes directly without re-serializing.
+// This avoids double-encoding when promoting values from Redis to local cache.
+func (l *LRU) SetRaw(key string, raw []byte, ttl time.Duration) {
+	var expires time.Time
+	if ttl > 0 {
+		expires = time.Now().Add(ttl)
+	}
+
+	l.lock.Lock()
+	defer l.lock.Unlock()
+
+	if ent, ok := l.items[key]; ok {
+		l.evictList.MoveToFront(ent)
+		e := ent.Value.(*lruEntry)
+		e.value = raw
+		e.expires = expires
+		if e.generation != l.currentGeneration {
+			e.generation = l.currentGeneration
+			l.len++
+		}
+		return
+	}
+
+	ent := &lruEntry{key, raw, expires, l.currentGeneration}
+	entry := l.evictList.PushFront(ent)
+	l.items[key] = entry
+	l.len++
+
+	if l.evictList.Len() > l.size {
+		l.removeElement(l.evictList.Back())
+	}
+}
+
 func (l *LRU) Get(key string) (any, bool) {
 	val, err := l.getItem(key)
 	if err != nil {