refactor(auth): delegate access control to be-system

Remove Agent Desk users, roles, login sessions, tokens, and local permission persistence. Expose the backend as an embeddable ai-agent module with host-provided subject lookup and operation authorization callbacks, and complete the frontend/backend repository split.

internal/pkg/dto/response/auth_response.go

@@ -1,26 +1,5 @@
 package response
 
-import "agent-desk/internal/pkg/enums"
-
-type AuthUserResponse struct {
-	ID       int64        `json:"id"`
-	Username string       `json:"username"`
-	Nickname string       `json:"nickname"`
-	Avatar   string       `json:"avatar"`
-	Status   enums.Status `json:"status"`
-	Roles    []string     `json:"roles"`
-}
-
-type LoginResponse struct {
-	AccessToken string            `json:"accessToken"`
-	ExpiresAt   string            `json:"expiresAt"`
-	User        *AuthUserResponse `json:"user"`
-	Permissions []string          `json:"permissions"`
-	Roles       []string          `json:"roles"`
-}
-
 type PublicConfigResponse struct {
-	Language      string `json:"language"`
-	WxWorkEnabled bool   `json:"wxworkEnabled"`
-	OIDCEnabled   bool   `json:"oidcEnabled"`
+	Language string `json:"language"`
 }