fix(数据层): 修复数据完整性与仓储一致性问题

## 数据完整性修复 (fix-critical-data-integrity)
- 添加 error_translate.go 统一错误转换层
- 修复 nil 输入和 NotFound 错误处理
- 增强仓储层错误一致性

## 仓储一致性修复 (fix-high-repository-consistency)
- Group schema 添加 default_validity_days 字段
- Account schema 添加 proxy edge 关联
- 新增 UsageLog ent schema 定义
- 修复 UpdateBalance/UpdateConcurrency 受影响行数校验

## 数据卫生修复 (fix-medium-data-hygiene)
- UserSubscription 添加软删除支持 (SoftDeleteMixin)
- RedeemCode/Setting 添加硬删除策略文档
- account_groups/user_allowed_groups 的 created_at 声明 timestamptz
- 停止写入 legacy users.allowed_groups 列
- 新增迁移: 011-014 (索引优化、软删除、孤立数据审计、列清理)

## 测试补充
- 添加 UserSubscription 软删除测试
- 添加迁移回归测试
- 添加 NotFound 错误测试

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/ent/usersubscription_create.go

@@ -12,6 +12,7 @@ import (
 	"entgo.io/ent/dialect/sql/sqlgraph"
 	"entgo.io/ent/schema/field"
 	"github.com/Wei-Shaw/sub2api/ent/group"
+	"github.com/Wei-Shaw/sub2api/ent/usagelog"
 	"github.com/Wei-Shaw/sub2api/ent/user"
 	"github.com/Wei-Shaw/sub2api/ent/usersubscription"
 )
@@ -52,6 +53,20 @@ func (_c *UserSubscriptionCreate) SetNillableUpdatedAt(v *time.Time) *UserSubscr
 	return _c
 }
 
+// SetDeletedAt sets the "deleted_at" field.
+func (_c *UserSubscriptionCreate) SetDeletedAt(v time.Time) *UserSubscriptionCreate {
+	_c.mutation.SetDeletedAt(v)
+	return _c
+}
+
+// SetNillableDeletedAt sets the "deleted_at" field if the given value is not nil.
+func (_c *UserSubscriptionCreate) SetNillableDeletedAt(v *time.Time) *UserSubscriptionCreate {
+	if v != nil {
+		_c.SetDeletedAt(*v)
+	}
+	return _c
+}
+
 // SetUserID sets the "user_id" field.
 func (_c *UserSubscriptionCreate) SetUserID(v int64) *UserSubscriptionCreate {
 	_c.mutation.SetUserID(v)
@@ -245,6 +260,21 @@ func (_c *UserSubscriptionCreate) SetAssignedByUser(v *User) *UserSubscriptionCr
 	return _c.SetAssignedByUserID(v.ID)
 }
 
+// AddUsageLogIDs adds the "usage_logs" edge to the UsageLog entity by IDs.
+func (_c *UserSubscriptionCreate) AddUsageLogIDs(ids ...int64) *UserSubscriptionCreate {
+	_c.mutation.AddUsageLogIDs(ids...)
+	return _c
+}
+
+// AddUsageLogs adds the "usage_logs" edges to the UsageLog entity.
+func (_c *UserSubscriptionCreate) AddUsageLogs(v ...*UsageLog) *UserSubscriptionCreate {
+	ids := make([]int64, len(v))
+	for i := range v {
+		ids[i] = v[i].ID
+	}
+	return _c.AddUsageLogIDs(ids...)
+}
+
 // Mutation returns the UserSubscriptionMutation object of the builder.
 func (_c *UserSubscriptionCreate) Mutation() *UserSubscriptionMutation {
 	return _c.mutation
@@ -252,7 +282,9 @@ func (_c *UserSubscriptionCreate) Mutation() *UserSubscriptionMutation {
 
 // Save creates the UserSubscription in the database.
 func (_c *UserSubscriptionCreate) Save(ctx context.Context) (*UserSubscription, error) {
-	_c.defaults()
+	if err := _c.defaults(); err != nil {
+		return nil, err
+	}
 	return withHooks(ctx, _c.sqlSave, _c.mutation, _c.hooks)
 }
 
@@ -279,12 +311,18 @@ func (_c *UserSubscriptionCreate) ExecX(ctx context.Context) {
 }
 
 // defaults sets the default values of the builder before save.
-func (_c *UserSubscriptionCreate) defaults() {
+func (_c *UserSubscriptionCreate) defaults() error {
 	if _, ok := _c.mutation.CreatedAt(); !ok {
+		if usersubscription.DefaultCreatedAt == nil {
+			return fmt.Errorf("ent: uninitialized usersubscription.DefaultCreatedAt (forgotten import ent/runtime?)")
+		}
 		v := usersubscription.DefaultCreatedAt()
 		_c.mutation.SetCreatedAt(v)
 	}
 	if _, ok := _c.mutation.UpdatedAt(); !ok {
+		if usersubscription.DefaultUpdatedAt == nil {
+			return fmt.Errorf("ent: uninitialized usersubscription.DefaultUpdatedAt (forgotten import ent/runtime?)")
+		}
 		v := usersubscription.DefaultUpdatedAt()
 		_c.mutation.SetUpdatedAt(v)
 	}
@@ -305,9 +343,13 @@ func (_c *UserSubscriptionCreate) defaults() {
 		_c.mutation.SetMonthlyUsageUsd(v)
 	}
 	if _, ok := _c.mutation.AssignedAt(); !ok {
+		if usersubscription.DefaultAssignedAt == nil {
+			return fmt.Errorf("ent: uninitialized usersubscription.DefaultAssignedAt (forgotten import ent/runtime?)")
+		}
 		v := usersubscription.DefaultAssignedAt()
 		_c.mutation.SetAssignedAt(v)
 	}
+	return nil
 }
 
 // check runs all checks and user-defined validators on the builder.
@@ -391,6 +433,10 @@ func (_c *UserSubscriptionCreate) createSpec() (*UserSubscription, *sqlgraph.Cre
 		_spec.SetField(usersubscription.FieldUpdatedAt, field.TypeTime, value)
 		_node.UpdatedAt = value
 	}
+	if value, ok := _c.mutation.DeletedAt(); ok {
+		_spec.SetField(usersubscription.FieldDeletedAt, field.TypeTime, value)
+		_node.DeletedAt = &value
+	}
 	if value, ok := _c.mutation.StartsAt(); ok {
 		_spec.SetField(usersubscription.FieldStartsAt, field.TypeTime, value)
 		_node.StartsAt = value
@@ -486,6 +532,22 @@ func (_c *UserSubscriptionCreate) createSpec() (*UserSubscription, *sqlgraph.Cre
 		_node.AssignedBy = &nodes[0]
 		_spec.Edges = append(_spec.Edges, edge)
 	}
+	if nodes := _c.mutation.UsageLogsIDs(); len(nodes) > 0 {
+		edge := &sqlgraph.EdgeSpec{
+			Rel:     sqlgraph.O2M,
+			Inverse: false,
+			Table:   usersubscription.UsageLogsTable,
+			Columns: []string{usersubscription.UsageLogsColumn},
+			Bidi:    false,
+			Target: &sqlgraph.EdgeTarget{
+				IDSpec: sqlgraph.NewFieldSpec(usagelog.FieldID, field.TypeInt64),
+			},
+		}
+		for _, k := range nodes {
+			edge.Target.Nodes = append(edge.Target.Nodes, k)
+		}
+		_spec.Edges = append(_spec.Edges, edge)
+	}
 	return _node, _spec
 }
 
@@ -550,6 +612,24 @@ func (u *UserSubscriptionUpsert) UpdateUpdatedAt() *UserSubscriptionUpsert {
 	return u
 }
 
+// SetDeletedAt sets the "deleted_at" field.
+func (u *UserSubscriptionUpsert) SetDeletedAt(v time.Time) *UserSubscriptionUpsert {
+	u.Set(usersubscription.FieldDeletedAt, v)
+	return u
+}
+
+// UpdateDeletedAt sets the "deleted_at" field to the value that was provided on create.
+func (u *UserSubscriptionUpsert) UpdateDeletedAt() *UserSubscriptionUpsert {
+	u.SetExcluded(usersubscription.FieldDeletedAt)
+	return u
+}
+
+// ClearDeletedAt clears the value of the "deleted_at" field.
+func (u *UserSubscriptionUpsert) ClearDeletedAt() *UserSubscriptionUpsert {
+	u.SetNull(usersubscription.FieldDeletedAt)
+	return u
+}
+
 // SetUserID sets the "user_id" field.
 func (u *UserSubscriptionUpsert) SetUserID(v int64) *UserSubscriptionUpsert {
 	u.Set(usersubscription.FieldUserID, v)
@@ -825,6 +905,27 @@ func (u *UserSubscriptionUpsertOne) UpdateUpdatedAt() *UserSubscriptionUpsertOne
 	})
 }
 
+// SetDeletedAt sets the "deleted_at" field.
+func (u *UserSubscriptionUpsertOne) SetDeletedAt(v time.Time) *UserSubscriptionUpsertOne {
+	return u.Update(func(s *UserSubscriptionUpsert) {
+		s.SetDeletedAt(v)
+	})
+}
+
+// UpdateDeletedAt sets the "deleted_at" field to the value that was provided on create.
+func (u *UserSubscriptionUpsertOne) UpdateDeletedAt() *UserSubscriptionUpsertOne {
+	return u.Update(func(s *UserSubscriptionUpsert) {
+		s.UpdateDeletedAt()
+	})
+}
+
+// ClearDeletedAt clears the value of the "deleted_at" field.
+func (u *UserSubscriptionUpsertOne) ClearDeletedAt() *UserSubscriptionUpsertOne {
+	return u.Update(func(s *UserSubscriptionUpsert) {
+		s.ClearDeletedAt()
+	})
+}
+
 // SetUserID sets the "user_id" field.
 func (u *UserSubscriptionUpsertOne) SetUserID(v int64) *UserSubscriptionUpsertOne {
 	return u.Update(func(s *UserSubscriptionUpsert) {
@@ -1302,6 +1403,27 @@ func (u *UserSubscriptionUpsertBulk) UpdateUpdatedAt() *UserSubscriptionUpsertBu
 	})
 }
 
+// SetDeletedAt sets the "deleted_at" field.
+func (u *UserSubscriptionUpsertBulk) SetDeletedAt(v time.Time) *UserSubscriptionUpsertBulk {
+	return u.Update(func(s *UserSubscriptionUpsert) {
+		s.SetDeletedAt(v)
+	})
+}
+
+// UpdateDeletedAt sets the "deleted_at" field to the value that was provided on create.
+func (u *UserSubscriptionUpsertBulk) UpdateDeletedAt() *UserSubscriptionUpsertBulk {
+	return u.Update(func(s *UserSubscriptionUpsert) {
+		s.UpdateDeletedAt()
+	})
+}
+
+// ClearDeletedAt clears the value of the "deleted_at" field.
+func (u *UserSubscriptionUpsertBulk) ClearDeletedAt() *UserSubscriptionUpsertBulk {
+	return u.Update(func(s *UserSubscriptionUpsert) {
+		s.ClearDeletedAt()
+	})
+}
+
 // SetUserID sets the "user_id" field.
 func (u *UserSubscriptionUpsertBulk) SetUserID(v int64) *UserSubscriptionUpsertBulk {
 	return u.Update(func(s *UserSubscriptionUpsert) {