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/dto/group_dto.go

@@ -0,0 +1,119 @@
+package dto
+
+// ==================== Group DTOs ====================
+// 从 dto.go 拆分而来：群组相关的请求与响应 DTO。
+// 与 group_converter.go 同属群组域。
+
+// CreateGroupRequest 创建群组请求
+type CreateGroupRequest struct {
+	Name        string   `json:"name" binding:"required,max=50"`
+	Description string   `json:"description" binding:"max=500"`
+	MemberIDs   []string `json:"member_ids"`
+}
+
+// UpdateGroupRequest 更新群组请求
+type UpdateGroupRequest struct {
+	Name        string `json:"name" binding:"omitempty,max=50"`
+	Description string `json:"description" binding:"omitempty,max=500"`
+	Avatar      string `json:"avatar" binding:"omitempty,url"`
+}
+
+// InviteMembersRequest 邀请成员请求
+type InviteMembersRequest struct {
+	MemberIDs []string `json:"member_ids" binding:"required,min=1"`
+}
+
+// TransferOwnerRequest 转让群主请求
+type TransferOwnerRequest struct {
+	NewOwnerID string `json:"new_owner_id" binding:"required"`
+}
+
+// SetRoleRequest 设置角色请求
+type SetRoleRequest struct {
+	Role string `json:"role" binding:"required,oneof=admin member"`
+}
+
+// SetNicknameRequest 设置昵称请求
+type SetNicknameRequest struct {
+	Nickname string `json:"nickname" binding:"max=50"`
+}
+
+// MuteMemberRequest 禁言成员请求
+type MuteMemberRequest struct {
+	Muted bool `json:"muted"`
+}
+
+// SetMuteAllRequest 设置全员禁言请求
+type SetMuteAllRequest struct {
+	MuteAll bool `json:"mute_all"`
+}
+
+// SetJoinTypeRequest 设置加群方式请求
+type SetJoinTypeRequest struct {
+	JoinType int `json:"join_type" binding:"min=0,max=2"`
+}
+
+// CreateAnnouncementRequest 创建群公告请求
+type CreateAnnouncementRequest struct {
+	Content string `json:"content" binding:"required,max=2000"`
+}
+
+// GroupResponse 群组响应
+type GroupResponse struct {
+	ID          string `json:"id"`
+	Name        string `json:"name"`
+	Avatar      string `json:"avatar"`
+	Description string `json:"description"`
+	OwnerID     string `json:"owner_id"`
+	MemberCount int    `json:"member_count"`
+	MaxMembers  int    `json:"max_members"`
+	JoinType    int    `json:"join_type"`
+	MuteAll     bool   `json:"mute_all"`
+	CreatedAt   string `json:"created_at"`
+}
+
+// GroupMemberResponse 群成员响应
+type GroupMemberResponse struct {
+	ID       string        `json:"id"`
+	GroupID  string        `json:"group_id"`
+	UserID   string        `json:"user_id"`
+	Role     string        `json:"role"`
+	Nickname string        `json:"nickname"`
+	Muted    bool          `json:"muted"`
+	JoinTime string        `json:"join_time"`
+	User     *UserResponse `json:"user,omitempty"`
+}
+
+// GroupAnnouncementResponse 群公告响应
+type GroupAnnouncementResponse struct {
+	ID        string `json:"id"`
+	GroupID   string `json:"group_id"`
+	Content   string `json:"content"`
+	AuthorID  string `json:"author_id"`
+	IsPinned  bool   `json:"is_pinned"`
+	CreatedAt string `json:"created_at"`
+}
+
+// GroupListResponse 群组列表响应
+type GroupListResponse struct {
+	List     []*GroupResponse `json:"list"`
+	Total    int64            `json:"total"`
+	Page     int              `json:"page"`
+	PageSize int              `json:"page_size"`
+}
+
+// GroupMemberListResponse 群成员列表响应
+type GroupMemberListResponse struct {
+	List     []*GroupMemberResponse `json:"list"`
+	Total    int64                  `json:"total"`
+	Page     int                    `json:"page"`
+	PageSize int                    `json:"page_size"`
+}
+
+// GroupAnnouncementListResponse 群公告列表响应
+type GroupAnnouncementListResponse struct {
+	List     []*GroupAnnouncementResponse `json:"list"`
+	Total    int64                        `json:"total"`
+	Page     int                          `json:"page"`
+	PageSize int                          `json:"page_size"`
+}