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/api/tracker/infrastructure/src/lib/mongo/issue-reminders.repository.ts

@@ -0,0 +1,63 @@
+import { Injectable } from '@nestjs/common';
+import { InjectModel } from '@nestjs/mongoose';
+import {
+  IssueReminder,
+  IssueRemindersRepository,
+} from '@task-stream/api/tracker/application';
+import { Model } from 'mongoose';
+import { ReadModels } from './read-model.schemas';
+
+type Stored = IssueReminder & { _id?: unknown };
+
+const strip = ({ _id: _ignored, ...reminder }: Stored): IssueReminder =>
+  reminder;
+
+@Injectable()
+export class MongoIssueRemindersRepository extends IssueRemindersRepository {
+  constructor(
+    @InjectModel(ReadModels.IssueReminder)
+    private readonly reminders: Model<Stored>,
+  ) {
+    super();
+  }
+
+  async save(reminder: IssueReminder): Promise<void> {
+    await this.remove(reminder.userId, reminder.issueId);
+    await this.reminders.create(reminder);
+  }
+
+  async waitingFor(
+    userId: string,
+    issueId: string,
+  ): Promise<IssueReminder | null> {
+    const doc = await this.reminders
+      .findOne({ userId, issueId, sentAt: null })
+      .lean<Stored>();
+    return doc ? strip(doc) : null;
+  }
+
+  async waitingOf(userId: string): Promise<IssueReminder[]> {
+    const docs = await this.reminders
+      .find({ userId, sentAt: null })
+      .sort({ at: 1 })
+      .lean<Stored[]>();
+    return docs.map(strip);
+  }
+
+  async remove(userId: string, issueId: string): Promise<void> {
+    await this.reminders.deleteMany({ userId, issueId, sentAt: null });
+  }
+
+  async due(now: string, limit: number): Promise<IssueReminder[]> {
+    const docs = await this.reminders
+      .find({ sentAt: null, at: { $lte: now } })
+      .sort({ at: 1 })
+      .limit(limit)
+      .lean<Stored[]>();
+    return docs.map(strip);
+  }
+
+  async markSent(id: string, at: string): Promise<void> {
+    await this.reminders.updateOne({ id }, { $set: { sentAt: at } });
+  }
+}