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/account/account.go

@@ -59,6 +59,10 @@ const (
 	FieldSessionWindowStatus = "session_window_status"
 	// EdgeGroups holds the string denoting the groups edge name in mutations.
 	EdgeGroups = "groups"
+	// EdgeProxy holds the string denoting the proxy edge name in mutations.
+	EdgeProxy = "proxy"
+	// EdgeUsageLogs holds the string denoting the usage_logs edge name in mutations.
+	EdgeUsageLogs = "usage_logs"
 	// EdgeAccountGroups holds the string denoting the account_groups edge name in mutations.
 	EdgeAccountGroups = "account_groups"
 	// Table holds the table name of the account in the database.
@@ -68,6 +72,20 @@ const (
 	// GroupsInverseTable is the table name for the Group entity.
 	// It exists in this package in order to avoid circular dependency with the "group" package.
 	GroupsInverseTable = "groups"
+	// ProxyTable is the table that holds the proxy relation/edge.
+	ProxyTable = "accounts"
+	// ProxyInverseTable is the table name for the Proxy entity.
+	// It exists in this package in order to avoid circular dependency with the "proxy" package.
+	ProxyInverseTable = "proxies"
+	// ProxyColumn is the table column denoting the proxy relation/edge.
+	ProxyColumn = "proxy_id"
+	// UsageLogsTable is the table that holds the usage_logs relation/edge.
+	UsageLogsTable = "usage_logs"
+	// UsageLogsInverseTable is the table name for the UsageLog entity.
+	// It exists in this package in order to avoid circular dependency with the "usagelog" package.
+	UsageLogsInverseTable = "usage_logs"
+	// UsageLogsColumn is the table column denoting the usage_logs relation/edge.
+	UsageLogsColumn = "account_id"
 	// AccountGroupsTable is the table that holds the account_groups relation/edge.
 	AccountGroupsTable = "account_groups"
 	// AccountGroupsInverseTable is the table name for the AccountGroup entity.
@@ -274,6 +292,27 @@ func ByGroups(term sql.OrderTerm, terms ...sql.OrderTerm) OrderOption {
 	}
 }
 
+// ByProxyField orders the results by proxy field.
+func ByProxyField(field string, opts ...sql.OrderTermOption) OrderOption {
+	return func(s *sql.Selector) {
+		sqlgraph.OrderByNeighborTerms(s, newProxyStep(), sql.OrderByField(field, opts...))
+	}
+}
+
+// ByUsageLogsCount orders the results by usage_logs count.
+func ByUsageLogsCount(opts ...sql.OrderTermOption) OrderOption {
+	return func(s *sql.Selector) {
+		sqlgraph.OrderByNeighborsCount(s, newUsageLogsStep(), opts...)
+	}
+}
+
+// ByUsageLogs orders the results by usage_logs terms.
+func ByUsageLogs(term sql.OrderTerm, terms ...sql.OrderTerm) OrderOption {
+	return func(s *sql.Selector) {
+		sqlgraph.OrderByNeighborTerms(s, newUsageLogsStep(), append([]sql.OrderTerm{term}, terms...)...)
+	}
+}
+
 // ByAccountGroupsCount orders the results by account_groups count.
 func ByAccountGroupsCount(opts ...sql.OrderTermOption) OrderOption {
 	return func(s *sql.Selector) {
@@ -294,6 +333,20 @@ func newGroupsStep() *sqlgraph.Step {
 		sqlgraph.Edge(sqlgraph.M2M, false, GroupsTable, GroupsPrimaryKey...),
 	)
 }
+func newProxyStep() *sqlgraph.Step {
+	return sqlgraph.NewStep(
+		sqlgraph.From(Table, FieldID),
+		sqlgraph.To(ProxyInverseTable, FieldID),
+		sqlgraph.Edge(sqlgraph.M2O, false, ProxyTable, ProxyColumn),
+	)
+}
+func newUsageLogsStep() *sqlgraph.Step {
+	return sqlgraph.NewStep(
+		sqlgraph.From(Table, FieldID),
+		sqlgraph.To(UsageLogsInverseTable, FieldID),
+		sqlgraph.Edge(sqlgraph.O2M, false, UsageLogsTable, UsageLogsColumn),
+	)
+}
 func newAccountGroupsStep() *sqlgraph.Step {
 	return sqlgraph.NewStep(
 		sqlgraph.From(Table, FieldID),

backend/ent/account/where.go

@@ -495,26 +495,6 @@ func ProxyIDNotIn(vs ...int64) predicate.Account {
 	return predicate.Account(sql.FieldNotIn(FieldProxyID, vs...))
 }
 
-// ProxyIDGT applies the GT predicate on the "proxy_id" field.
-func ProxyIDGT(v int64) predicate.Account {
-	return predicate.Account(sql.FieldGT(FieldProxyID, v))
-}
-
-// ProxyIDGTE applies the GTE predicate on the "proxy_id" field.
-func ProxyIDGTE(v int64) predicate.Account {
-	return predicate.Account(sql.FieldGTE(FieldProxyID, v))
-}
-
-// ProxyIDLT applies the LT predicate on the "proxy_id" field.
-func ProxyIDLT(v int64) predicate.Account {
-	return predicate.Account(sql.FieldLT(FieldProxyID, v))
-}
-
-// ProxyIDLTE applies the LTE predicate on the "proxy_id" field.
-func ProxyIDLTE(v int64) predicate.Account {
-	return predicate.Account(sql.FieldLTE(FieldProxyID, v))
-}
-
 // ProxyIDIsNil applies the IsNil predicate on the "proxy_id" field.
 func ProxyIDIsNil() predicate.Account {
 	return predicate.Account(sql.FieldIsNull(FieldProxyID))
@@ -1153,6 +1133,52 @@ func HasGroupsWith(preds ...predicate.Group) predicate.Account {
 	})
 }
 
+// HasProxy applies the HasEdge predicate on the "proxy" edge.
+func HasProxy() predicate.Account {
+	return predicate.Account(func(s *sql.Selector) {
+		step := sqlgraph.NewStep(
+			sqlgraph.From(Table, FieldID),
+			sqlgraph.Edge(sqlgraph.M2O, false, ProxyTable, ProxyColumn),
+		)
+		sqlgraph.HasNeighbors(s, step)
+	})
+}
+
+// HasProxyWith applies the HasEdge predicate on the "proxy" edge with a given conditions (other predicates).
+func HasProxyWith(preds ...predicate.Proxy) predicate.Account {
+	return predicate.Account(func(s *sql.Selector) {
+		step := newProxyStep()
+		sqlgraph.HasNeighborsWith(s, step, func(s *sql.Selector) {
+			for _, p := range preds {
+				p(s)
+			}
+		})
+	})
+}
+
+// HasUsageLogs applies the HasEdge predicate on the "usage_logs" edge.
+func HasUsageLogs() predicate.Account {
+	return predicate.Account(func(s *sql.Selector) {
+		step := sqlgraph.NewStep(
+			sqlgraph.From(Table, FieldID),
+			sqlgraph.Edge(sqlgraph.O2M, false, UsageLogsTable, UsageLogsColumn),
+		)
+		sqlgraph.HasNeighbors(s, step)
+	})
+}
+
+// HasUsageLogsWith applies the HasEdge predicate on the "usage_logs" edge with a given conditions (other predicates).
+func HasUsageLogsWith(preds ...predicate.UsageLog) predicate.Account {
+	return predicate.Account(func(s *sql.Selector) {
+		step := newUsageLogsStep()
+		sqlgraph.HasNeighborsWith(s, step, func(s *sql.Selector) {
+			for _, p := range preds {
+				p(s)
+			}
+		})
+	})
+}
+
 // HasAccountGroups applies the HasEdge predicate on the "account_groups" edge.
 func HasAccountGroups() predicate.Account {
 	return predicate.Account(func(s *sql.Selector) {