chore: initial public snapshot for github upload

llm-gateway-competitors/sub2api-tar/backend/migrations/053_add_security_secrets.sql

@@ -0,0 +1,10 @@
+-- 存储系统级密钥（如 JWT 签名密钥、TOTP 加密密钥）
+CREATE TABLE IF NOT EXISTS security_secrets (
+  id BIGSERIAL PRIMARY KEY,
+  key VARCHAR(100) NOT NULL UNIQUE,
+  value TEXT NOT NULL,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_security_secrets_key ON security_secrets (key);