stage-9: heartbeat system with periodic checks

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

src/main.py

@@ -64,6 +64,33 @@ def main():
     scheduler = Scheduler(send_callback=_send_to_channel, config=config)
     client.scheduler = scheduler  # type: ignore[attr-defined]
 
+    # Heartbeat: register as periodic job if enabled
+    hb_config = config.get("heartbeat", {})
+    if hb_config.get("enabled"):
+        from src.heartbeat import run_heartbeat
+
+        interval_min = hb_config.get("interval_minutes", 30)
+
+        async def _heartbeat_tick() -> None:
+            """Run heartbeat and log result."""
+            try:
+                result = await asyncio.to_thread(run_heartbeat)
+                logger.info("Heartbeat: %s", result)
+            except Exception as exc:
+                logger.error("Heartbeat failed: %s", exc)
+
+        from apscheduler.triggers.interval import IntervalTrigger
+
+        scheduler._scheduler.add_job(
+            _heartbeat_tick,
+            trigger=IntervalTrigger(minutes=interval_min),
+            id="__heartbeat__",
+            max_instances=1,
+        )
+        logger.info(
+            "Heartbeat registered (every %d min)", interval_min
+        )
+
     # PID file
     PID_FILE.write_text(str(os.getpid()))