feat(auth): add org/dept/position management, user page, and Phase 2 completion

Complete Phase 2 identity & authentication module:
- Organization CRUD with tree structure (parent_id + materialized path)
- Department CRUD nested under organizations with tree support
- Position CRUD nested under departments
- User management page with table, create/edit modal, role assignment
- Organization architecture page with 3-panel tree layout
- Frontend API layer for orgs/depts/positions
- Sidebar navigation updated with organization menu item
- Fix parse_ttl edge case for strings ending in 'd' (e.g. "invalid")

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

@@ -1,3 +1,4 @@
 pub mod auth_handler;
+pub mod org_handler;
 pub mod role_handler;
 pub mod user_handler;