feat(rpm): RPM 限流模块优化

P0:
- rpm_override 嵌入 Auth Cache Snapshot，消除每请求 DB 查询 (snapshot v6→v7)
- 429 RPM 响应返回 Retry-After 头（当前分钟剩余秒数）

P1:
- ClearAll 按钮直连 DELETE API，带 loading 防重复
- 新增 GET /admin/users/:id/rpm-status 管理员 RPM 用量查询端点

优化:
- checkRPM 从级联互斥改为并行取最严，user.rpm_limit 作为全局硬上限始终生效
- Override/Group 变更后自动失效 auth cache
- fail-open 语义不变，Redis 故障不阻塞业务

backend/ent/user_create.go

@@ -325,6 +325,20 @@ func (_c *UserCreate) SetNillableTotalRecharged(v *float64) *UserCreate {
 	return _c
 }
 
+// SetRpmLimit sets the "rpm_limit" field.
+func (_c *UserCreate) SetRpmLimit(v int) *UserCreate {
+	_c.mutation.SetRpmLimit(v)
+	return _c
+}
+
+// SetNillableRpmLimit sets the "rpm_limit" field if the given value is not nil.
+func (_c *UserCreate) SetNillableRpmLimit(v *int) *UserCreate {
+	if v != nil {
+		_c.SetRpmLimit(*v)
+	}
+	return _c
+}
+
 // AddAPIKeyIDs adds the "api_keys" edge to the APIKey entity by IDs.
 func (_c *UserCreate) AddAPIKeyIDs(ids ...int64) *UserCreate {
 	_c.mutation.AddAPIKeyIDs(ids...)
@@ -604,6 +618,10 @@ func (_c *UserCreate) defaults() error {
 		v := user.DefaultTotalRecharged
 		_c.mutation.SetTotalRecharged(v)
 	}
+	if _, ok := _c.mutation.RpmLimit(); !ok {
+		v := user.DefaultRpmLimit
+		_c.mutation.SetRpmLimit(v)
+	}
 	return nil
 }
 
@@ -687,6 +705,9 @@ func (_c *UserCreate) check() error {
 	if _, ok := _c.mutation.TotalRecharged(); !ok {
 		return &ValidationError{Name: "total_recharged", err: errors.New(`ent: missing required field "User.total_recharged"`)}
 	}
+	if _, ok := _c.mutation.RpmLimit(); !ok {
+		return &ValidationError{Name: "rpm_limit", err: errors.New(`ent: missing required field "User.rpm_limit"`)}
+	}
 	return nil
 }
 
@@ -802,6 +823,10 @@ func (_c *UserCreate) createSpec() (*User, *sqlgraph.CreateSpec) {
 		_spec.SetField(user.FieldTotalRecharged, field.TypeFloat64, value)
 		_node.TotalRecharged = value
 	}
+	if value, ok := _c.mutation.RpmLimit(); ok {
+		_spec.SetField(user.FieldRpmLimit, field.TypeInt, value)
+		_node.RpmLimit = value
+	}
 	if nodes := _c.mutation.APIKeysIDs(); len(nodes) > 0 {
 		edge := &sqlgraph.EdgeSpec{
 			Rel:     sqlgraph.O2M,
@@ -1362,6 +1387,24 @@ func (u *UserUpsert) AddTotalRecharged(v float64) *UserUpsert {
 	return u
 }
 
+// SetRpmLimit sets the "rpm_limit" field.
+func (u *UserUpsert) SetRpmLimit(v int) *UserUpsert {
+	u.Set(user.FieldRpmLimit, v)
+	return u
+}
+
+// UpdateRpmLimit sets the "rpm_limit" field to the value that was provided on create.
+func (u *UserUpsert) UpdateRpmLimit() *UserUpsert {
+	u.SetExcluded(user.FieldRpmLimit)
+	return u
+}
+
+// AddRpmLimit adds v to the "rpm_limit" field.
+func (u *UserUpsert) AddRpmLimit(v int) *UserUpsert {
+	u.Add(user.FieldRpmLimit, v)
+	return u
+}
+
 // UpdateNewValues updates the mutable fields using the new values that were set on create.
 // Using this option is equivalent to using:
 //
@@ -1771,6 +1814,27 @@ func (u *UserUpsertOne) UpdateTotalRecharged() *UserUpsertOne {
 	})
 }
 
+// SetRpmLimit sets the "rpm_limit" field.
+func (u *UserUpsertOne) SetRpmLimit(v int) *UserUpsertOne {
+	return u.Update(func(s *UserUpsert) {
+		s.SetRpmLimit(v)
+	})
+}
+
+// AddRpmLimit adds v to the "rpm_limit" field.
+func (u *UserUpsertOne) AddRpmLimit(v int) *UserUpsertOne {
+	return u.Update(func(s *UserUpsert) {
+		s.AddRpmLimit(v)
+	})
+}
+
+// UpdateRpmLimit sets the "rpm_limit" field to the value that was provided on create.
+func (u *UserUpsertOne) UpdateRpmLimit() *UserUpsertOne {
+	return u.Update(func(s *UserUpsert) {
+		s.UpdateRpmLimit()
+	})
+}
+
 // Exec executes the query.
 func (u *UserUpsertOne) Exec(ctx context.Context) error {
 	if len(u.create.conflict) == 0 {
@@ -2346,6 +2410,27 @@ func (u *UserUpsertBulk) UpdateTotalRecharged() *UserUpsertBulk {
 	})
 }
 
+// SetRpmLimit sets the "rpm_limit" field.
+func (u *UserUpsertBulk) SetRpmLimit(v int) *UserUpsertBulk {
+	return u.Update(func(s *UserUpsert) {
+		s.SetRpmLimit(v)
+	})
+}
+
+// AddRpmLimit adds v to the "rpm_limit" field.
+func (u *UserUpsertBulk) AddRpmLimit(v int) *UserUpsertBulk {
+	return u.Update(func(s *UserUpsert) {
+		s.AddRpmLimit(v)
+	})
+}
+
+// UpdateRpmLimit sets the "rpm_limit" field to the value that was provided on create.
+func (u *UserUpsertBulk) UpdateRpmLimit() *UserUpsertBulk {
+	return u.Update(func(s *UserUpsert) {
+		s.UpdateRpmLimit()
+	})
+}
+
 // Exec executes the query.
 func (u *UserUpsertBulk) Exec(ctx context.Context) error {
 	if u.create.err != nil {