feat(api): add all REST route handlers and display-api test (Task 12)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

display/middleware/src/api/routes/mqtt-topics.ts

@@ -0,0 +1,57 @@
+import { Router } from 'express';
+import {
+  getTopicsForBroker,
+  updateTopic,
+  startDiscovery,
+  addManualTopic,
+} from '../../modules/mqtt/topic-discovery';
+
+const router = Router({ mergeParams: true });
+
+// GET /api/mqtt/brokers/:brokerId/topics
+router.get('/', (req, res): void => {
+  try {
+    const brokerId = parseInt(req.params.brokerId);
+    res.json(getTopicsForBroker(brokerId));
+  } catch (err) {
+    res.status(500).json({ error: (err as Error).message });
+  }
+});
+
+// PUT /api/mqtt/brokers/:brokerId/topics/:id
+router.put('/:id', (req, res): void => {
+  try {
+    const topic = updateTopic(parseInt(req.params.id), req.body);
+    if (!topic) { res.status(404).json({ error: 'Topic not found' }); return; }
+    res.json(topic);
+  } catch (err) {
+    res.status(500).json({ error: (err as Error).message });
+  }
+});
+
+// POST /api/mqtt/brokers/:brokerId/topics/discover
+router.post('/discover', (req, res): void => {
+  const brokerId = parseInt(req.params.brokerId);
+  const { prefix } = req.body;
+
+  res.json({ message: 'Discovery started', brokerId, prefix: prefix ?? null });
+
+  // Run in background
+  startDiscovery(brokerId, prefix).catch((err) => {
+    console.error('Discovery error:', (err as Error).message);
+  });
+});
+
+// POST /api/mqtt/brokers/:brokerId/topics/manual
+router.post('/manual', (req, res): void => {
+  try {
+    const brokerId = parseInt(req.params.brokerId);
+    const { topic } = req.body;
+    if (!topic) { res.status(400).json({ error: 'topic is required' }); return; }
+    res.status(201).json(addManualTopic(brokerId, topic));
+  } catch (err) {
+    res.status(500).json({ error: (err as Error).message });
+  }
+});
+
+export default router;