feat(fp): flush pending autosave before navigation/unload

Close the last-mile autosave gap: a debounced edit made in the final <600ms
before leaving a page was lost — the wizard draft-sync timer is cleared on
destroy without flushing, and root stores keep an armed timer the teardown
ignores.

New `shared/application/pending-saves.ts`: a root `PendingSaves` registry every
autosave owner joins (BriefStore, OrgTemplateStore, each createDraftSync). Two
seams flush through it — `flushPendingGuard` (CanDeactivate, on the five
autosave routes) awaits the pending write before an in-app route change; a
`beforeunload` handler (provideUnloadFlush) fires it best-effort and raises the
browser's native unsaved-changes prompt. ponytail: the HTTP seam is Angular
HttpClient (no keepalive/sendBeacon), so a hard-close flush can't be guaranteed
— hence the prompt; upgrade path noted in a comment. Each owner now nulls its
timer handle on fire so `hasPendingSave()` is accurate, and exposes
`flushPending()`.

Verified live against the running stack: navigating away 91ms after a keystroke
(well inside the debounce) fires one PUT /brief before the route changes; a
dirty reload raises the prompt, a clean reload does not. FE lint / check:tokens
/ 299 tests (+11) / build / build-storybook green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/app.routes.ts

@@ -1,6 +1,7 @@
 import { Routes } from '@angular/router';
 import { ShellComponent } from '@shared/layout/shell/shell.component';
 import { authGuard, capabilityGuard } from '@auth/auth.guard';
+import { flushPendingGuard } from '@shared/application/pending-saves';
 
 export const routes: Routes = [
   {
@@ -32,23 +33,28 @@ export const routes: Routes = [
       {
         path: 'registreren',
         canActivate: [authGuard],
+        // Autosave wizard: flush the pending debounced draft before leaving (pending-saves.ts).
+        canDeactivate: [flushPendingGuard],
         loadComponent: () =>
           import('@registratie/ui/registratie.page').then((m) => m.RegistratiePage),
       },
       {
         path: 'herregistratie',
         canActivate: [authGuard],
+        canDeactivate: [flushPendingGuard],
         loadComponent: () =>
           import('@herregistratie/ui/herregistratie.page').then((m) => m.HerregistratiePage),
       },
       {
         path: 'intake',
         canActivate: [authGuard],
+        canDeactivate: [flushPendingGuard],
         loadComponent: () => import('@herregistratie/ui/intake.page').then((m) => m.IntakePage),
       },
       {
         path: 'brief',
         canActivate: [authGuard],
+        canDeactivate: [flushPendingGuard],
         loadComponent: () => import('@brief/ui/brief.page').then((m) => m.BriefPage),
       },
       {
@@ -57,6 +63,7 @@ export const routes: Routes = [
         // unless GET /me resolved `orgtemplate:edit` (Admin role). Backend re-enforces
         // via the OrgAdmin gate — the guard just avoids loading a page that would 403.
         canActivate: [capabilityGuard('orgtemplate:edit')],
+        canDeactivate: [flushPendingGuard],
         loadComponent: () =>
           import('@brief/ui/org-template.page').then((m) => m.OrgTemplatePage),
       },