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/presenters/src/lib/ui/notifications-bell.ts

@@ -28,6 +28,7 @@ const ICON: Record<NotificationKind, string> = {
   [NotificationKind.COMMENTED]: 'chat',
   [NotificationKind.MENTIONED]: 'chat',
   [NotificationKind.REPLIED]: 'chat',
+  [NotificationKind.PROPOSED]: 'light-bulb',
   [NotificationKind.WATCHED]: 'focus',
   [NotificationKind.ADDED_TO_PROJECT]: 'briefcase',
   [NotificationKind.REMINDER]: 'calendar',