feat(auth): 实现 TOTP 双因素认证功能

新增功能：
- 支持 Google Authenticator 等应用进行 TOTP 二次验证
- 用户可在个人设置中启用/禁用 2FA
- 登录时支持 TOTP 验证流程
- 管理后台可全局开关 TOTP 功能

安全增强：
- TOTP 密钥使用 AES-256-GCM 加密存储
- 添加 TOTP_ENCRYPTION_KEY 配置项，必须手动配置才能启用功能
- 防止服务重启导致加密密钥变更使用户无法登录
- 验证失败次数限制，防止暴力破解

配置说明：
- Docker 部署：在 .env 中设置 TOTP_ENCRYPTION_KEY
- 非 Docker 部署：在 config.yaml 中设置 totp.encryption_key
- 生成密钥命令：openssl rand -hex 32

backend/ent/user/user.go

@@ -37,6 +37,12 @@ const (
 	FieldUsername = "username"
 	// FieldNotes holds the string denoting the notes field in the database.
 	FieldNotes = "notes"
+	// FieldTotpSecretEncrypted holds the string denoting the totp_secret_encrypted field in the database.
+	FieldTotpSecretEncrypted = "totp_secret_encrypted"
+	// FieldTotpEnabled holds the string denoting the totp_enabled field in the database.
+	FieldTotpEnabled = "totp_enabled"
+	// FieldTotpEnabledAt holds the string denoting the totp_enabled_at field in the database.
+	FieldTotpEnabledAt = "totp_enabled_at"
 	// EdgeAPIKeys holds the string denoting the api_keys edge name in mutations.
 	EdgeAPIKeys = "api_keys"
 	// EdgeRedeemCodes holds the string denoting the redeem_codes edge name in mutations.
@@ -134,6 +140,9 @@ var Columns = []string{
 	FieldStatus,
 	FieldUsername,
 	FieldNotes,
+	FieldTotpSecretEncrypted,
+	FieldTotpEnabled,
+	FieldTotpEnabledAt,
 }
 
 var (
@@ -188,6 +197,8 @@ var (
 	UsernameValidator func(string) error
 	// DefaultNotes holds the default value on creation for the "notes" field.
 	DefaultNotes string
+	// DefaultTotpEnabled holds the default value on creation for the "totp_enabled" field.
+	DefaultTotpEnabled bool
 )
 
 // OrderOption defines the ordering options for the User queries.
@@ -253,6 +264,21 @@ func ByNotes(opts ...sql.OrderTermOption) OrderOption {
 	return sql.OrderByField(FieldNotes, opts...).ToFunc()
 }
 
+// ByTotpSecretEncrypted orders the results by the totp_secret_encrypted field.
+func ByTotpSecretEncrypted(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldTotpSecretEncrypted, opts...).ToFunc()
+}
+
+// ByTotpEnabled orders the results by the totp_enabled field.
+func ByTotpEnabled(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldTotpEnabled, opts...).ToFunc()
+}
+
+// ByTotpEnabledAt orders the results by the totp_enabled_at field.
+func ByTotpEnabledAt(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldTotpEnabledAt, opts...).ToFunc()
+}
+
 // ByAPIKeysCount orders the results by api_keys count.
 func ByAPIKeysCount(opts ...sql.OrderTermOption) OrderOption {
 	return func(s *sql.Selector) {

backend/ent/user/where.go

@@ -110,6 +110,21 @@ func Notes(v string) predicate.User {
 	return predicate.User(sql.FieldEQ(FieldNotes, v))
 }
 
+// TotpSecretEncrypted applies equality check predicate on the "totp_secret_encrypted" field. It's identical to TotpSecretEncryptedEQ.
+func TotpSecretEncrypted(v string) predicate.User {
+	return predicate.User(sql.FieldEQ(FieldTotpSecretEncrypted, v))
+}
+
+// TotpEnabled applies equality check predicate on the "totp_enabled" field. It's identical to TotpEnabledEQ.
+func TotpEnabled(v bool) predicate.User {
+	return predicate.User(sql.FieldEQ(FieldTotpEnabled, v))
+}
+
+// TotpEnabledAt applies equality check predicate on the "totp_enabled_at" field. It's identical to TotpEnabledAtEQ.
+func TotpEnabledAt(v time.Time) predicate.User {
+	return predicate.User(sql.FieldEQ(FieldTotpEnabledAt, v))
+}
+
 // CreatedAtEQ applies the EQ predicate on the "created_at" field.
 func CreatedAtEQ(v time.Time) predicate.User {
 	return predicate.User(sql.FieldEQ(FieldCreatedAt, v))
@@ -710,6 +725,141 @@ func NotesContainsFold(v string) predicate.User {
 	return predicate.User(sql.FieldContainsFold(FieldNotes, v))
 }
 
+// TotpSecretEncryptedEQ applies the EQ predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedEQ(v string) predicate.User {
+	return predicate.User(sql.FieldEQ(FieldTotpSecretEncrypted, v))
+}
+
+// TotpSecretEncryptedNEQ applies the NEQ predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedNEQ(v string) predicate.User {
+	return predicate.User(sql.FieldNEQ(FieldTotpSecretEncrypted, v))
+}
+
+// TotpSecretEncryptedIn applies the In predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedIn(vs ...string) predicate.User {
+	return predicate.User(sql.FieldIn(FieldTotpSecretEncrypted, vs...))
+}
+
+// TotpSecretEncryptedNotIn applies the NotIn predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedNotIn(vs ...string) predicate.User {
+	return predicate.User(sql.FieldNotIn(FieldTotpSecretEncrypted, vs...))
+}
+
+// TotpSecretEncryptedGT applies the GT predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedGT(v string) predicate.User {
+	return predicate.User(sql.FieldGT(FieldTotpSecretEncrypted, v))
+}
+
+// TotpSecretEncryptedGTE applies the GTE predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedGTE(v string) predicate.User {
+	return predicate.User(sql.FieldGTE(FieldTotpSecretEncrypted, v))
+}
+
+// TotpSecretEncryptedLT applies the LT predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedLT(v string) predicate.User {
+	return predicate.User(sql.FieldLT(FieldTotpSecretEncrypted, v))
+}
+
+// TotpSecretEncryptedLTE applies the LTE predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedLTE(v string) predicate.User {
+	return predicate.User(sql.FieldLTE(FieldTotpSecretEncrypted, v))
+}
+
+// TotpSecretEncryptedContains applies the Contains predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedContains(v string) predicate.User {
+	return predicate.User(sql.FieldContains(FieldTotpSecretEncrypted, v))
+}
+
+// TotpSecretEncryptedHasPrefix applies the HasPrefix predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedHasPrefix(v string) predicate.User {
+	return predicate.User(sql.FieldHasPrefix(FieldTotpSecretEncrypted, v))
+}
+
+// TotpSecretEncryptedHasSuffix applies the HasSuffix predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedHasSuffix(v string) predicate.User {
+	return predicate.User(sql.FieldHasSuffix(FieldTotpSecretEncrypted, v))
+}
+
+// TotpSecretEncryptedIsNil applies the IsNil predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedIsNil() predicate.User {
+	return predicate.User(sql.FieldIsNull(FieldTotpSecretEncrypted))
+}
+
+// TotpSecretEncryptedNotNil applies the NotNil predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedNotNil() predicate.User {
+	return predicate.User(sql.FieldNotNull(FieldTotpSecretEncrypted))
+}
+
+// TotpSecretEncryptedEqualFold applies the EqualFold predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedEqualFold(v string) predicate.User {
+	return predicate.User(sql.FieldEqualFold(FieldTotpSecretEncrypted, v))
+}
+
+// TotpSecretEncryptedContainsFold applies the ContainsFold predicate on the "totp_secret_encrypted" field.
+func TotpSecretEncryptedContainsFold(v string) predicate.User {
+	return predicate.User(sql.FieldContainsFold(FieldTotpSecretEncrypted, v))
+}
+
+// TotpEnabledEQ applies the EQ predicate on the "totp_enabled" field.
+func TotpEnabledEQ(v bool) predicate.User {
+	return predicate.User(sql.FieldEQ(FieldTotpEnabled, v))
+}
+
+// TotpEnabledNEQ applies the NEQ predicate on the "totp_enabled" field.
+func TotpEnabledNEQ(v bool) predicate.User {
+	return predicate.User(sql.FieldNEQ(FieldTotpEnabled, v))
+}
+
+// TotpEnabledAtEQ applies the EQ predicate on the "totp_enabled_at" field.
+func TotpEnabledAtEQ(v time.Time) predicate.User {
+	return predicate.User(sql.FieldEQ(FieldTotpEnabledAt, v))
+}
+
+// TotpEnabledAtNEQ applies the NEQ predicate on the "totp_enabled_at" field.
+func TotpEnabledAtNEQ(v time.Time) predicate.User {
+	return predicate.User(sql.FieldNEQ(FieldTotpEnabledAt, v))
+}
+
+// TotpEnabledAtIn applies the In predicate on the "totp_enabled_at" field.
+func TotpEnabledAtIn(vs ...time.Time) predicate.User {
+	return predicate.User(sql.FieldIn(FieldTotpEnabledAt, vs...))
+}
+
+// TotpEnabledAtNotIn applies the NotIn predicate on the "totp_enabled_at" field.
+func TotpEnabledAtNotIn(vs ...time.Time) predicate.User {
+	return predicate.User(sql.FieldNotIn(FieldTotpEnabledAt, vs...))
+}
+
+// TotpEnabledAtGT applies the GT predicate on the "totp_enabled_at" field.
+func TotpEnabledAtGT(v time.Time) predicate.User {
+	return predicate.User(sql.FieldGT(FieldTotpEnabledAt, v))
+}
+
+// TotpEnabledAtGTE applies the GTE predicate on the "totp_enabled_at" field.
+func TotpEnabledAtGTE(v time.Time) predicate.User {
+	return predicate.User(sql.FieldGTE(FieldTotpEnabledAt, v))
+}
+
+// TotpEnabledAtLT applies the LT predicate on the "totp_enabled_at" field.
+func TotpEnabledAtLT(v time.Time) predicate.User {
+	return predicate.User(sql.FieldLT(FieldTotpEnabledAt, v))
+}
+
+// TotpEnabledAtLTE applies the LTE predicate on the "totp_enabled_at" field.
+func TotpEnabledAtLTE(v time.Time) predicate.User {
+	return predicate.User(sql.FieldLTE(FieldTotpEnabledAt, v))
+}
+
+// TotpEnabledAtIsNil applies the IsNil predicate on the "totp_enabled_at" field.
+func TotpEnabledAtIsNil() predicate.User {
+	return predicate.User(sql.FieldIsNull(FieldTotpEnabledAt))
+}
+
+// TotpEnabledAtNotNil applies the NotNil predicate on the "totp_enabled_at" field.
+func TotpEnabledAtNotNil() predicate.User {
+	return predicate.User(sql.FieldNotNull(FieldTotpEnabledAt))
+}
+
 // HasAPIKeys applies the HasEdge predicate on the "api_keys" edge.
 func HasAPIKeys() predicate.User {
 	return predicate.User(func(s *sql.Selector) {