feat: «Recordármelo», a reminder of a ticket only for me

On a ticket, «Recordármelo» offers in an hour, this evening, tomorrow or
next Monday at 9, in a week, or any date and time, with an optional note.
The ticket shows the waiting one («Te lo recordaré el mié 21 a las 9:00»)
to change or drop. Every minute a scheduler tells the ones whose time
came as a REMINDER notification (bell, push, e-mail), once, and forgets
those whose ticket went to the trash or out of reach. One per person and
ticket, private, no history (Mongo `issue_reminders`).

API: setReminder / clearReminder, Issue.myReminder, myReminders;
PUT/DELETE /api/issues/{issue}/reminder, GET /api/me/reminders. MCP:
remind_me.

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

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

@@ -120,6 +120,17 @@ export class IssueFacade {
     );
   }
 
+  /** Remind me of the ticket then (null: drop it); one per ticket. */
+  setReminder(at: string | null, note: string | null = null): void {
+    this.withIssue((issueId) =>
+      this.dispatch.reminderRequested({
+        issueId,
+        at,
+        note: note?.trim() || null,
+      }),
+    );
+  }
+
   /** Follow the ticket with everything under it (an epic), or stop. */
   setFollowingTree(on: boolean): void {
     this.withIssue((issueId) =>