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/shared/infrastructure/src/lib/realtime-connection.ts

@@ -0,0 +1,20 @@
+import { Injectable } from '@angular/core';
+import { Observable, Subject } from 'rxjs';
+
+/**
+ * The state of the subscriptions' socket that the app cares about: when it
+ * comes back after a cut. Whatever happened meanwhile was not received, so
+ * views reload when it does.
+ */
+@Injectable({ providedIn: 'root' })
+export class RealtimeConnection {
+  private readonly back = new Subject<void>();
+
+  /** Each time the socket reconnects (not the first time it connects). */
+  readonly reconnected$: Observable<void> = this.back.asObservable();
+
+  /** Called by the GraphQL client. */
+  reconnected(): void {
+    this.back.next();
+  }
+}