fix: address review feedback for per-group queue reliability

- Fix startup recovery running before WhatsApp connects, which could
  permanently lose agent responses by advancing lastAgentTimestamp
  before sock is initialized
- Add 5s retry on container failure so messages aren't silently dropped
  until a new message arrives for the group
- Use `container stop` in shutdown instead of raw SIGTERM to CLI wrapper,
  ensuring proper container cleanup
- Replace unnecessary dynamic imports with static imports in processTaskIpc
- Guard JSON.parse of DB-stored last_agent_timestamp against corruption
- Validate MAX_CONCURRENT_CONTAINERS (default 5, min 1, NaN-safe)

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

src/task-scheduler.ts

@@ -26,7 +26,7 @@ export interface SchedulerDependencies {
   registeredGroups: () => Record<string, RegisteredGroup>;
   getSessions: () => Record<string, string>;
   queue: GroupQueue;
-  onProcess: (groupJid: string, proc: ChildProcess) => void;
+  onProcess: (groupJid: string, proc: ChildProcess, containerName: string) => void;
 }
 
 async function runTask(
@@ -98,7 +98,7 @@ async function runTask(
         chatJid: task.chat_jid,
         isMain,
       },
-      (proc) => deps.onProcess(task.chat_jid, proc),
+      (proc, containerName) => deps.onProcess(task.chat_jid, proc, containerName),
     );
 
     if (output.status === 'error') {