feat(auth): make upload review a separate grant instead of an admin privilege

Reviewing the upload queue is now a per-user flag (reviews_uploads), not part
of the admin role: several people can hold it, a moderator can have it, and an
admin may not. Only admins grant or revoke it; existing admins keep it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

services/api/internal/auth/store.go

@@ -31,10 +31,11 @@ type UserFilter struct {
 
 // UserUpdate — изменения из админки. nil — не менять.
 type UserUpdate struct {
-	DisplayName  **string
-	Role         *Role
-	IsBlocked    *bool
-	RevokeTokens bool
+	DisplayName    **string
+	Role           *Role
+	IsBlocked      *bool
+	ReviewsUploads *bool
+	RevokeTokens   bool
 }
 
 // Store — доступ к users, refresh_tokens, audit_log и app_settings.