feat: steadier live updates and notices for public proposals

- The web pings the live connection, reconnects when it goes quiet and
  reloads what each screen shows after reconnecting.
- Dropping a card on a column it cannot go to puts it back.
- Owners and admins get a notice when a proposal arrives.
- The proposal limit lives in Redis, so it holds across instances.
- REST tells whether I voted; pasted images leave the attachment list.
- Deleting a project removes its Git integration; no lint warnings left.
- Reactions and the blocked badge are components of their own.
- Docs: what is done and what is left (chapter 10), Word and PDF.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/web/tracker/domain/src/lib/ports/gateways.ts

@@ -370,4 +370,9 @@ export abstract class TrackerRealtimeGateway {
   abstract projectChanges(projectId: string): Observable<ProjectChanged>;
   abstract myProjectsChanges(): Observable<ProjectChanged>;
   abstract notifications(): Observable<Notification>;
+  /**
+   * Each time the live connection comes back after a cut: what happened
+   * meanwhile was not received, so views reload.
+   */
+  abstract reconnects(): Observable<void>;
 }