feat: per-group queue, SQLite state, graceful shutdown

Add per-group container locking with global concurrency limit to prevent
concurrent containers for the same group (#89) and cap total containers.
Fix message batching bug where lastAgentTimestamp advanced to trigger
message instead of latest in batch, causing redundant re-processing.
Move router state, sessions, and registered groups from JSON files to
SQLite with automatic one-time migration. Add SIGTERM/SIGINT handlers
with graceful shutdown (SIGTERM -> grace period -> SIGKILL). Add startup
recovery for messages missed during crash. Remove dead code: utils.ts,
Session type, isScheduledTask flag, ContainerConfig.env, getTaskRunLogs,
GroupQueue.isActive.

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

src/task-scheduler.ts

@@ -1,9 +1,9 @@
+import { ChildProcess } from 'child_process';
 import { CronExpressionParser } from 'cron-parser';
 import fs from 'fs';
 import path from 'path';
 
 import {
-  DATA_DIR,
   GROUPS_DIR,
   MAIN_GROUP_FOLDER,
   SCHEDULER_POLL_INTERVAL,
@@ -17,6 +17,7 @@ import {
   logTaskRun,
   updateTaskAfterRun,
 } from './db.js';
+import { GroupQueue } from './group-queue.js';
 import { logger } from './logger.js';
 import { RegisteredGroup, ScheduledTask } from './types.js';
 
@@ -24,6 +25,8 @@ export interface SchedulerDependencies {
   sendMessage: (jid: string, text: string) => Promise<void>;
   registeredGroups: () => Record<string, RegisteredGroup>;
   getSessions: () => Record<string, string>;
+  queue: GroupQueue;
+  onProcess: (groupJid: string, proc: ChildProcess) => void;
 }
 
 async function runTask(
@@ -86,14 +89,17 @@ async function runTask(
     task.context_mode === 'group' ? sessions[task.group_folder] : undefined;
 
   try {
-    const output = await runContainerAgent(group, {
-      prompt: task.prompt,
-      sessionId,
-      groupFolder: task.group_folder,
-      chatJid: task.chat_jid,
-      isMain,
-      isScheduledTask: true,
-    });
+    const output = await runContainerAgent(
+      group,
+      {
+        prompt: task.prompt,
+        sessionId,
+        groupFolder: task.group_folder,
+        chatJid: task.chat_jid,
+        isMain,
+      },
+      (proc) => deps.onProcess(task.chat_jid, proc),
+    );
 
     if (output.status === 'error') {
       error = output.error || 'Unknown error';
@@ -165,7 +171,11 @@ export function startSchedulerLoop(deps: SchedulerDependencies): void {
           continue;
         }
 
-        await runTask(currentTask, deps);
+        deps.queue.enqueueTask(
+          currentTask.chat_jid,
+          currentTask.id,
+          () => runTask(currentTask, deps),
+        );
       }
     } catch (err) {
       logger.error({ err }, 'Error in scheduler loop');