fix(saas): migration idempotency fixes + SCHEMA_VERSION bump to 14

- Add IF NOT EXISTS to accounts_template_assignment ALTER COLUMN
- Add IF NOT EXISTS to webhooks CREATE INDEX statements
- Add created_at/updated_at columns + ON CONFLICT DO NOTHING to industry templates
- Bump SCHEMA_VERSION 13→14 to force migration re-run on existing DB

crates/zclaw-saas/src/db.rs

@@ -5,7 +5,7 @@ use sqlx::PgPool;
 use crate::config::DatabaseConfig;
 use crate::error::SaasResult;
 
-const SCHEMA_VERSION: i32 = 13;
+const SCHEMA_VERSION: i32 = 14;
 
 /// 初始化数据库
 pub async fn init_db(config: &DatabaseConfig) -> SaasResult<PgPool> {