refactor(server): decouple services and improve architecture

- Introduce interfaces for all major services (JWT, PostAI, Comment, Message, Notification, QRCodeLogin, Upload, Vote, etc.) to support dependency inversion.
- Move query parameters from `internal/dto` to a new `internal/query` package to separate request payloads from data transfer objects.
- Refactor `internal/router` to use embedded `RouterDeps` for cleaner dependency management.
- Decouple handlers from repositories by injecting services instead of direct repository access, ensuring proper layering.
- Improve database initialization by moving it from `internal/model` to `internal/database`.
- Optimize message decryption by implementing a more efficient `BatchDecrypt` method in `MessageEncryptor` using a worker pool.
- Enhance error handling and security by implementing fail-fast checks for encryption key length during startup.
- Clean up unused code, including the `avatar` package and several unused DTOs.

internal/cache/seq_buffer.go

@@ -94,17 +94,6 @@ func (m *SeqBufferManager) IsEnabled() bool {
 	return m.config.Enabled && m.rdb != nil
 }
 
-// NewSeqBufferManagerFromCache 从 ConversationCache 的 Cache 接口创建 SeqBufferManager
-func NewSeqBufferManagerFromCache(cacheBackend Cache, cfg SeqBufferConfig, repo ConversationRepository, msgRepo MessageRepository) *SeqBufferManager {
-	redisCache, ok := cacheBackend.(*RedisCache)
-	if !ok {
-		zap.L().Warn("SeqBuffer: cache is not RedisCache, seq pre-allocation disabled")
-		return &SeqBufferManager{config: cfg, repo: repo, msgRepo: msgRepo}
-	}
-	rdb := redisCache.GetRedisClient().GetClient()
-	return NewSeqBufferManager(rdb, cfg, repo, msgRepo)
-}
-
 // NewSeqBufferManagerFromRedisPkg 从 pkg/redis.Client 创建 SeqBufferManager
 func NewSeqBufferManagerFromRedisPkg(redisPkgClient *redisPkg.Client, cfg SeqBufferConfig, repo ConversationRepository, msgRepo MessageRepository) *SeqBufferManager {
 	if redisPkgClient == nil {