feat(admin): add drag-and-drop group sort order

- Add `sort_order` field to groups table with migration
- Add `PUT /api/v1/admin/groups/sort-order` API for batch update
- Implement drag-and-drop UI using vue-draggable-plus
- All queries now order groups by sort_order
- Add i18n support (en/zh) for sort-related UI text
- Update test stubs to satisfy new interface methods

backend/ent/group_create.go

@@ -340,6 +340,20 @@ func (_c *GroupCreate) SetSupportedModelScopes(v []string) *GroupCreate {
 	return _c
 }
 
+// SetSortOrder sets the "sort_order" field.
+func (_c *GroupCreate) SetSortOrder(v int) *GroupCreate {
+	_c.mutation.SetSortOrder(v)
+	return _c
+}
+
+// SetNillableSortOrder sets the "sort_order" field if the given value is not nil.
+func (_c *GroupCreate) SetNillableSortOrder(v *int) *GroupCreate {
+	if v != nil {
+		_c.SetSortOrder(*v)
+	}
+	return _c
+}
+
 // AddAPIKeyIDs adds the "api_keys" edge to the APIKey entity by IDs.
 func (_c *GroupCreate) AddAPIKeyIDs(ids ...int64) *GroupCreate {
 	_c.mutation.AddAPIKeyIDs(ids...)
@@ -521,6 +535,10 @@ func (_c *GroupCreate) defaults() error {
 		v := group.DefaultSupportedModelScopes
 		_c.mutation.SetSupportedModelScopes(v)
 	}
+	if _, ok := _c.mutation.SortOrder(); !ok {
+		v := group.DefaultSortOrder
+		_c.mutation.SetSortOrder(v)
+	}
 	return nil
 }
 
@@ -585,6 +603,9 @@ func (_c *GroupCreate) check() error {
 	if _, ok := _c.mutation.SupportedModelScopes(); !ok {
 		return &ValidationError{Name: "supported_model_scopes", err: errors.New(`ent: missing required field "Group.supported_model_scopes"`)}
 	}
+	if _, ok := _c.mutation.SortOrder(); !ok {
+		return &ValidationError{Name: "sort_order", err: errors.New(`ent: missing required field "Group.sort_order"`)}
+	}
 	return nil
 }
 
@@ -708,6 +729,10 @@ func (_c *GroupCreate) createSpec() (*Group, *sqlgraph.CreateSpec) {
 		_spec.SetField(group.FieldSupportedModelScopes, field.TypeJSON, value)
 		_node.SupportedModelScopes = value
 	}
+	if value, ok := _c.mutation.SortOrder(); ok {
+		_spec.SetField(group.FieldSortOrder, field.TypeInt, value)
+		_node.SortOrder = value
+	}
 	if nodes := _c.mutation.APIKeysIDs(); len(nodes) > 0 {
 		edge := &sqlgraph.EdgeSpec{
 			Rel:     sqlgraph.O2M,
@@ -1266,6 +1291,24 @@ func (u *GroupUpsert) UpdateSupportedModelScopes() *GroupUpsert {
 	return u
 }
 
+// SetSortOrder sets the "sort_order" field.
+func (u *GroupUpsert) SetSortOrder(v int) *GroupUpsert {
+	u.Set(group.FieldSortOrder, v)
+	return u
+}
+
+// UpdateSortOrder sets the "sort_order" field to the value that was provided on create.
+func (u *GroupUpsert) UpdateSortOrder() *GroupUpsert {
+	u.SetExcluded(group.FieldSortOrder)
+	return u
+}
+
+// AddSortOrder adds v to the "sort_order" field.
+func (u *GroupUpsert) AddSortOrder(v int) *GroupUpsert {
+	u.Add(group.FieldSortOrder, v)
+	return u
+}
+
 // UpdateNewValues updates the mutable fields using the new values that were set on create.
 // Using this option is equivalent to using:
 //
@@ -1780,6 +1823,27 @@ func (u *GroupUpsertOne) UpdateSupportedModelScopes() *GroupUpsertOne {
 	})
 }
 
+// SetSortOrder sets the "sort_order" field.
+func (u *GroupUpsertOne) SetSortOrder(v int) *GroupUpsertOne {
+	return u.Update(func(s *GroupUpsert) {
+		s.SetSortOrder(v)
+	})
+}
+
+// AddSortOrder adds v to the "sort_order" field.
+func (u *GroupUpsertOne) AddSortOrder(v int) *GroupUpsertOne {
+	return u.Update(func(s *GroupUpsert) {
+		s.AddSortOrder(v)
+	})
+}
+
+// UpdateSortOrder sets the "sort_order" field to the value that was provided on create.
+func (u *GroupUpsertOne) UpdateSortOrder() *GroupUpsertOne {
+	return u.Update(func(s *GroupUpsert) {
+		s.UpdateSortOrder()
+	})
+}
+
 // Exec executes the query.
 func (u *GroupUpsertOne) Exec(ctx context.Context) error {
 	if len(u.create.conflict) == 0 {
@@ -2460,6 +2524,27 @@ func (u *GroupUpsertBulk) UpdateSupportedModelScopes() *GroupUpsertBulk {
 	})
 }
 
+// SetSortOrder sets the "sort_order" field.
+func (u *GroupUpsertBulk) SetSortOrder(v int) *GroupUpsertBulk {
+	return u.Update(func(s *GroupUpsert) {
+		s.SetSortOrder(v)
+	})
+}
+
+// AddSortOrder adds v to the "sort_order" field.
+func (u *GroupUpsertBulk) AddSortOrder(v int) *GroupUpsertBulk {
+	return u.Update(func(s *GroupUpsert) {
+		s.AddSortOrder(v)
+	})
+}
+
+// UpdateSortOrder sets the "sort_order" field to the value that was provided on create.
+func (u *GroupUpsertBulk) UpdateSortOrder() *GroupUpsertBulk {
+	return u.Update(func(s *GroupUpsert) {
+		s.UpdateSortOrder()
+	})
+}
+
 // Exec executes the query.
 func (u *GroupUpsertBulk) Exec(ctx context.Context) error {
 	if u.create.err != nil {