feat(admin): Worker scaling controls via k8s API

- Add /api/k8s/workers endpoint to get deployment status
- Add /api/k8s/workers/scale endpoint to scale replicas (0-50)
- Add worker scaling UI to Tasks Dashboard (+/- 5 workers)
- Shows ready/desired replica count
- Uses in-cluster config in k8s, kubeconfig locally

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/src/routes/k8s.ts

@@ -0,0 +1,144 @@
+/**
+ * Kubernetes Control Routes
+ *
+ * Provides admin UI control over k8s resources like worker scaling.
+ * Uses in-cluster config when running in k8s, or kubeconfig locally.
+ */
+
+import { Router, Request, Response } from 'express';
+import * as k8s from '@kubernetes/client-node';
+
+const router = Router();
+
+// K8s client setup - lazy initialization
+let appsApi: k8s.AppsV1Api | null = null;
+let k8sError: string | null = null;
+
+function getK8sClient(): k8s.AppsV1Api | null {
+  if (appsApi) return appsApi;
+  if (k8sError) return null;
+
+  try {
+    const kc = new k8s.KubeConfig();
+
+    // Try in-cluster config first (when running in k8s)
+    try {
+      kc.loadFromCluster();
+      console.log('[K8s] Loaded in-cluster config');
+    } catch {
+      // Fall back to default kubeconfig (local dev)
+      try {
+        kc.loadFromDefault();
+        console.log('[K8s] Loaded default kubeconfig');
+      } catch (e) {
+        k8sError = 'No k8s config available';
+        console.log('[K8s] No config available - k8s routes disabled');
+        return null;
+      }
+    }
+
+    appsApi = kc.makeApiClient(k8s.AppsV1Api);
+    return appsApi;
+  } catch (e: any) {
+    k8sError = e.message;
+    console.error('[K8s] Failed to initialize client:', e.message);
+    return null;
+  }
+}
+
+const NAMESPACE = process.env.K8S_NAMESPACE || 'dispensary-scraper';
+const WORKER_DEPLOYMENT = 'scraper-worker';
+
+/**
+ * GET /api/k8s/workers
+ * Get current worker deployment status
+ */
+router.get('/workers', async (_req: Request, res: Response) => {
+  const client = getK8sClient();
+
+  if (!client) {
+    return res.json({
+      success: true,
+      available: false,
+      error: k8sError || 'K8s not available',
+      replicas: 0,
+      readyReplicas: 0,
+    });
+  }
+
+  try {
+    const deployment = await client.readNamespacedDeployment({
+      name: WORKER_DEPLOYMENT,
+      namespace: NAMESPACE,
+    });
+
+    res.json({
+      success: true,
+      available: true,
+      replicas: deployment.spec?.replicas || 0,
+      readyReplicas: deployment.status?.readyReplicas || 0,
+      availableReplicas: deployment.status?.availableReplicas || 0,
+      updatedReplicas: deployment.status?.updatedReplicas || 0,
+    });
+  } catch (e: any) {
+    console.error('[K8s] Error getting deployment:', e.message);
+    res.status(500).json({
+      success: false,
+      error: e.message,
+    });
+  }
+});
+
+/**
+ * POST /api/k8s/workers/scale
+ * Scale worker deployment
+ * Body: { replicas: number }
+ */
+router.post('/workers/scale', async (req: Request, res: Response) => {
+  const client = getK8sClient();
+
+  if (!client) {
+    return res.status(503).json({
+      success: false,
+      error: k8sError || 'K8s not available',
+    });
+  }
+
+  const { replicas } = req.body;
+
+  if (typeof replicas !== 'number' || replicas < 0 || replicas > 50) {
+    return res.status(400).json({
+      success: false,
+      error: 'replicas must be a number between 0 and 50',
+    });
+  }
+
+  try {
+    // Patch the deployment to set replicas
+    await client.patchNamespacedDeploymentScale({
+      name: WORKER_DEPLOYMENT,
+      namespace: NAMESPACE,
+      body: {
+        spec: { replicas },
+      },
+    }, undefined, undefined, undefined, undefined, undefined, {
+      headers: { 'Content-Type': 'application/strategic-merge-patch+json' },
+    });
+
+    console.log(`[K8s] Scaled ${WORKER_DEPLOYMENT} to ${replicas} replicas`);
+
+    res.json({
+      success: true,
+      replicas,
+      message: `Scaled to ${replicas} workers`,
+    });
+  } catch (e: any) {
+    console.error('[K8s] Error scaling deployment:', e.message);
+    res.status(500).json({
+      success: false,
+      error: e.message,
+    });
+  }
+});
+
+export default router;