fix(api): the API failed to start after moving the proposal limit to Redis

ProposalLimiter, in the presenters, asked for the RateLimitStore port,
which only the application layer sees, so Nest could not build it and
the container never became healthy. The count now lives in an
application service, ProposalQuota; the presenter only answers 429.

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

libs/api/tracker/application/src/lib/proposal-quota.service.spec.ts

@@ -0,0 +1,22 @@
+import { ProposalQuota } from './proposal-quota.service';
+import { RateLimitStore } from './ports/rate-limit.store';
+
+class MemoryStore extends RateLimitStore {
+  readonly counts = new Map<string, number>();
+  async hit(key: string): Promise<number> {
+    const count = (this.counts.get(key) ?? 0) + 1;
+    this.counts.set(key, count);
+    return count;
+  }
+}
+
+describe('ProposalQuota', () => {
+  it('lets five proposals through per address, then says no', async () => {
+    const quota = new ProposalQuota(new MemoryStore());
+    const answers = [];
+    for (let i = 0; i < 6; i++) answers.push(await quota.take('1.2.3.4'));
+
+    expect(answers).toEqual([true, true, true, true, true, false]);
+    expect(await quota.take('5.6.7.8')).toBe(true);
+  });
+});