feat(backend): Phase C.3 Zapier-compatible polling endpoint + event-types discovery

backend/src/modules/webhooks/routes.ts

@@ -108,4 +108,30 @@ export async function webhookRoutes(app: FastifyInstance) {
     const limit = parseInt((req.query as Record<string, string>).limit || '50', 10);
     return repo.listEvents(id, Math.min(limit, 100));
   });
+
+  // ── Zapier-compatible polling endpoint ─────────────────────
+  // GET /webhooks/zapier/poll?eventType=timer.fired
+  // Returns recent events for Zapier polling triggers
+  app.get('/webhooks/zapier/poll', async req => {
+    const auth = await extractAuth(req);
+    const q = req.query as Record<string, string>;
+    const eventType = q.eventType;
+    if (!eventType || !WEBHOOK_EVENT_TYPES.includes(eventType as (typeof WEBHOOK_EVENT_TYPES)[number])) {
+      throw new BadRequestError(`eventType query parameter must be one of: ${WEBHOOK_EVENT_TYPES.join(', ')}`);
+    }
+    const subs = await repo.listSubscriptions(auth.sub, PRODUCT_ID);
+    const matching = subs.filter(s => s.events.includes(eventType as (typeof WEBHOOK_EVENT_TYPES)[number]));
+    if (matching.length === 0) {
+      return { items: [] };
+    }
+    // Return events from all matching subscriptions
+    const allEvents = [];
+    for (const sub of matching) {
+      const events = await repo.listEvents(sub.id, 10);
+      allEvents.push(...events);
+    }
+    // Sort by creation time descending
+    allEvents.sort((a, b) => new Date(b.createdAt).getTime() - new Date(a.createdAt).getTime());
+    return { items: allEvents.slice(0, 25) };
+  });
 }