feat: Worker improvements and Run Now duplicate prevention

- Fix Run Now to prevent duplicate task creation
- Add loading state to Run Now button in UI
- Return early when no stores need refresh
- Worker dashboard improvements
- Browser pooling architecture updates
- K8s worker config updates (8 replicas, 3 concurrent tasks)

CLAUDE.md

@@ -25,13 +25,26 @@ Never import `src/db/migrate.ts` at runtime. Use `src/db/pool.ts` for DB access.
 - **Worker** = Concurrent task runner INSIDE a pod (controlled by `MAX_CONCURRENT_TASKS` env var)
 - Formula: `8 pods × MAX_CONCURRENT_TASKS = total concurrent workers`
 
-**To increase workers:** Change `MAX_CONCURRENT_TASKS` env var, NOT replicas.
-```bash
-# CORRECT - increase workers per pod
-kubectl set env deployment/scraper-worker -n dispensary-scraper MAX_CONCURRENT_TASKS=5
+**Browser Task Memory Limits:**
+- Each Puppeteer/Chrome browser uses ~400 MB RAM
+- Pod memory limit is 2 GB
+- **MAX_CONCURRENT_TASKS=3** is the safe maximum for browser tasks
+- More than 3 concurrent browsers per pod = OOM crash
 
-# WRONG - never scale above 8 replicas
-kubectl scale deployment/scraper-worker --replicas=20  # NEVER DO THIS
+| Browsers | RAM Used | Status |
+|----------|----------|--------|
+| 3 | ~1.3 GB | Safe (recommended) |
+| 4 | ~1.7 GB | Risky |
+| 5+ | >2 GB | OOM crash |
+
+**To increase throughput:** Add more pods (up to 8), NOT more concurrent tasks per pod.
+
+```bash
+# CORRECT - scale pods (up to 8)
+kubectl scale deployment/scraper-worker -n dispensary-scraper --replicas=8
+
+# WRONG - will cause OOM crashes
+kubectl set env deployment/scraper-worker -n dispensary-scraper MAX_CONCURRENT_TASKS=10
 ```
 
 **If K8s API returns ServiceUnavailable:** STOP IMMEDIATELY. Do not retry. The cluster is overloaded.