feat(security): 启动时自动迁移并持久化JWT密钥

- 新增 security_secrets 表及 Ent schema 用于存储系统级密钥
- 启动阶段支持无 jwt.secret 配置并在数据库中自动生成持久化
- 在 Ent 初始化后补齐密钥并执行完整配置校验
- 增加并发与异常分支单元测试，覆盖密钥引导核心路径

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/ent/securitysecret/securitysecret.go

@@ -0,0 +1,86 @@
+// Code generated by ent, DO NOT EDIT.
+
+package securitysecret
+
+import (
+	"time"
+
+	"entgo.io/ent/dialect/sql"
+)
+
+const (
+	// Label holds the string label denoting the securitysecret type in the database.
+	Label = "security_secret"
+	// FieldID holds the string denoting the id field in the database.
+	FieldID = "id"
+	// FieldCreatedAt holds the string denoting the created_at field in the database.
+	FieldCreatedAt = "created_at"
+	// FieldUpdatedAt holds the string denoting the updated_at field in the database.
+	FieldUpdatedAt = "updated_at"
+	// FieldKey holds the string denoting the key field in the database.
+	FieldKey = "key"
+	// FieldValue holds the string denoting the value field in the database.
+	FieldValue = "value"
+	// Table holds the table name of the securitysecret in the database.
+	Table = "security_secrets"
+)
+
+// Columns holds all SQL columns for securitysecret fields.
+var Columns = []string{
+	FieldID,
+	FieldCreatedAt,
+	FieldUpdatedAt,
+	FieldKey,
+	FieldValue,
+}
+
+// ValidColumn reports if the column name is valid (part of the table columns).
+func ValidColumn(column string) bool {
+	for i := range Columns {
+		if column == Columns[i] {
+			return true
+		}
+	}
+	return false
+}
+
+var (
+	// DefaultCreatedAt holds the default value on creation for the "created_at" field.
+	DefaultCreatedAt func() time.Time
+	// DefaultUpdatedAt holds the default value on creation for the "updated_at" field.
+	DefaultUpdatedAt func() time.Time
+	// UpdateDefaultUpdatedAt holds the default value on update for the "updated_at" field.
+	UpdateDefaultUpdatedAt func() time.Time
+	// KeyValidator is a validator for the "key" field. It is called by the builders before save.
+	KeyValidator func(string) error
+	// ValueValidator is a validator for the "value" field. It is called by the builders before save.
+	ValueValidator func(string) error
+)
+
+// OrderOption defines the ordering options for the SecuritySecret queries.
+type OrderOption func(*sql.Selector)
+
+// ByID orders the results by the id field.
+func ByID(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldID, opts...).ToFunc()
+}
+
+// ByCreatedAt orders the results by the created_at field.
+func ByCreatedAt(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldCreatedAt, opts...).ToFunc()
+}
+
+// ByUpdatedAt orders the results by the updated_at field.
+func ByUpdatedAt(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldUpdatedAt, opts...).ToFunc()
+}
+
+// ByKey orders the results by the key field.
+func ByKey(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldKey, opts...).ToFunc()
+}
+
+// ByValue orders the results by the value field.
+func ByValue(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldValue, opts...).ToFunc()
+}