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/infrastructure/src/lib/adapters/graphql-issues.gateway.ts

@@ -43,9 +43,12 @@ import {
   SetIssueParentDocument,
   SetIssueReleaseDocument,
   UnlinkIssuesDocument,
+  UnpinIssueDocument,
   UnwatchIssueDocument,
   VoteIssueDocument,
   WatchIssueDocument,
+  MyPinsDocument,
+  PinIssueDocument,
   UpdateChecklistItemDocument,
   UpdateIssueDocument,
 } from '../graphql/generated';
@@ -192,6 +195,19 @@ export class GraphqlIssuesGateway extends IssuesGateway {
       .pipe(map((d) => toCommandResult(d.voteIssue)));
   }
 
+  pins(): Observable<IssueSummary[]> {
+    return this.gql
+      .query(MyPinsDocument, {})
+      .pipe(map((d) => d.myPins.map(toIssueSummary)));
+  }
+
+  pin(issueId: string, pinned: boolean): Observable<void> {
+    const done$: Observable<unknown> = pinned
+      ? this.gql.mutate(PinIssueDocument, { issueId })
+      : this.gql.mutate(UnpinIssueDocument, { issueId });
+    return done$.pipe(map(() => undefined));
+  }
+
   watch(issueId: string, watching: boolean): Observable<CommandResult> {
     return watching
       ? this.gql