refactor: introduce model layer for centralized data synchronization

Add hoover model.js as a central reactive store per subsystem, replacing
per-component data fetching with a single source of truth.

- Add hoover/model.js with modelRegister, modelFetch, and WS invalidation
- Refactor websocket.js to route messages to model refresh (drop per-component
  subscribe/unsubscribe)
- Simplify component.js by removing WS subscription management
- Add refresh option to apiSubmit, deprecate refactorLoad and checkAbort
- Rewrite all pages to use getModel() instead of inline data fetching
- Bootstrap model registrations in app.js
- Add GET /api/firewall/state endpoint
- Fix restart-services.sh restart order and add service health verification
- Update hoover.md docs with model layer architecture

webui/static/pages/notfound.js

@@ -1,12 +1,8 @@
-import { h, PageHeader, definePage } from '/static/hoover/index.js?v=6';
+import { h, PageHeader, definePage } from '/static/hoover/index.js?v=7';
 
 export default definePage({
     init() {
-        return { path: '' };
-    },
-    subscribe: [],
-    async load(state) {
-        state.path = location.hash.slice(1) || '';
+        return { path: location.hash.slice(1) || '' };
     },
     render(state) {
         return [