refactor(main): remove unused Python heartbeat in favor of cron job

Heartbeat is now handled exclusively by the Claude-based cron job
(heartbeat-2h in jobs.json), which is more flexible.

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

src/main.py

@@ -83,37 +83,6 @@ 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)
-        hb_channel = hb_config.get("channel", "echo-core")
-
-        async def _heartbeat_tick() -> None:
-            """Run heartbeat and send findings to channel."""
-            try:
-                result = await asyncio.to_thread(run_heartbeat, config)
-                logger.info("Heartbeat: %s", result)
-                if result and "HEARTBEAT_OK" not in result:
-                    await _send_to_channel(hb_channel, 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, channel: %s)",
-            interval_min, hb_channel,
-        )
-
     # Newsletter Cercetași checker (optional)
     newsletter_config = config.get("newsletter_cercetasi", {})
     if newsletter_config.get("enabled"):