feat(auth): add tenant seed data and bootstrap logic

- seed.rs: creates 21 permissions, admin+viewer roles, admin user with Argon2 password
- AuthConfig added to server config with default password Admin@2026
- Server startup: auto-creates default tenant and seeds auth data if not exists
- Idempotent: checks for existing tenant before seeding

crates/erp-auth/src/service/mod.rs

@@ -1,4 +1,5 @@
 pub mod auth_service;
 pub mod password;
+pub mod seed;
 pub mod token_service;
 pub mod user_service;