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/keys.go

@@ -44,7 +44,6 @@ const (
 	keyPrefixMsgSeq      = "msg_seq"    // Seq 计数器
 	keyPrefixMsgPage     = "msg_page"   // 分页缓存
 	keyPrefixMsgIdempotent = "msg_idem"  // 消息幂等键
-	keyPrefixSeqBuffer   = "seq_buf"    // Seq 预分配缓冲区 Hash
 )
 
 // PostListKey 生成帖子列表缓存键
@@ -198,12 +197,6 @@ func MessageIdempotentKey(senderID, clientMsgID string) string {
 	return fmt.Sprintf("%s:%s:%s", keyPrefixMsgIdempotent, senderID, clientMsgID)
 }
 
-// SeqBufferKey seq 预分配缓冲区 Hash key
-func SeqBufferKey(convID string) string {
-	return fmt.Sprintf("%s:%s", keyPrefixSeqBuffer, convID)
-}
-
-
 // UserReadSeqKey 用户已读位置缓存键（OpenIM 风格 SEQ_USER_READ:{convID}:{userID}）
 func UserReadSeqKey(convID, userID string) string {
 	return fmt.Sprintf("%s:%s:%s", PrefixUserReadSeq, convID, userID)