feat(tasks): 25 workers, pool starts paused by default

- Increase worker replicas from 5 to 25
- Task pool now starts PAUSED on deploy, admin must click Start Pool
- Prevents workers from grabbing tasks before system is ready

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

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

backend/src/tasks/task-pool-state.ts

@@ -6,10 +6,12 @@
  * task-service.ts and routes/tasks.ts.
  *
  * State is in-memory and resets on server restart.
- * By default, the pool is OPEN (not paused).
+ * By default, the pool is PAUSED (closed) - admin must explicitly start it.
+ * This prevents workers from immediately grabbing tasks on deploy before
+ * the system is ready.
  */
 
-let taskPoolPaused = false;
+let taskPoolPaused = true;
 
 export function isTaskPoolPaused(): boolean {
   return taskPoolPaused;