feat: initialize ERP base platform (extracted from HMS)

- Stripped 11 business crates (health, ai, dialysis, plugins)
- Cleaned AppState, AppConfig, main.rs from business coupling
- Reduced migrations from 169 to 53 (base-only)
- Removed health_provider trait from erp-core
- Removed business integration tests
- Removed gateway rate limiting middleware
- Base capabilities: auth, RBAC, JWT, config, workflow, message, plugin, audit, crypto, RLS, multi-tenant

Cargo check: OK
Cargo test: OK

crates/erp-server/tests/integration.rs

@@ -0,0 +1,8 @@
+#[path = "integration/auth_tests.rs"]
+mod auth_tests;
+#[path = "integration/plugin_tests.rs"]
+mod plugin_tests;
+#[path = "integration/test_db.rs"]
+mod test_db;
+#[path = "integration/workflow_tests.rs"]
+mod workflow_tests;