feat: pinned tickets, at hand on the home page and in search

Each person pins up to 20 tickets from the ticket's page («Fijar»). They
show as a strip under the projects on the home page and in the search
palette before typing. Private and without history, like the views of
«my work» (Mongo `pinned_issues`); tickets in the trash or out of reach
are left out, and when the list is full the unreadable ones are dropped
first.

API: GET /api/me/pins, PUT/DELETE /api/issues/{issue}/pin; GraphQL
myPins, pinIssue, unpinIssue and Issue.pinned.

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

libs/web/tracker/application/src/lib/facades/issue.facade.ts

@@ -120,6 +120,13 @@ export class IssueFacade {
     );
   }
 
+  /** Pin the ticket for me (or unpin it): at hand on my home page and in search. */
+  setPinned(pinned: boolean): void {
+    this.withIssue((issueId) =>
+      this.dispatch.pinRequested({ issueId, pinned }),
+    );
+  }
+
   /** Places the open ticket under another one by its key; null: back to the top. */
   /**
    * Tickets to link to or hang the open one from: the most recently updated