feat(config): add system configuration module (Phase 3)

Implement the complete erp-config crate with:
- Data dictionaries (CRUD + items management)
- Dynamic menus (tree structure with role filtering)
- System settings (hierarchical: platform > tenant > org > user)
- Numbering rules (concurrency-safe via PostgreSQL advisory_lock)
- Theme and language configuration (via settings store)
- 6 database migrations (dictionaries, menus, settings, numbering_rules)
- Frontend Settings page with 5 tabs (dictionary, menu, numbering, settings, theme)

Refactor: move RBAC functions (require_permission) from erp-auth to erp-core
to avoid cross-module dependencies.

Add 20 new seed permissions for config module operations.

crates/erp-server/src/state.rs

@@ -50,3 +50,13 @@ impl FromRef<AppState> for erp_auth::AuthState {
         }
     }
 }
+
+/// Allow erp-config handlers to extract their required state without depending on erp-server.
+impl FromRef<AppState> for erp_config::ConfigState {
+    fn from_ref(state: &AppState) -> Self {
+        Self {
+            db: state.db.clone(),
+            event_bus: state.event_bus.clone(),
+        }
+    }
+}