feat: implement continuous polling loop

start() now loops indefinitely, calling poll() every 5 minutes.
Each cycle is wrapped in a poll_cycle OTel span with a
flights.published attribute (0 on failure). Transient poll failures
are logged and the loop continues. The Kafka stream engine is stopped
cleanly via try/finally on shutdown.

Closes #5

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main.py

@@ -1,3 +1,4 @@
+import asyncio
 import json
 import logging
 
@@ -16,6 +17,8 @@ from settings import KafkaSettings, OtelSettings, SchipholApiSettings
 
 logger = logging.getLogger(__name__)
 
+POLL_INTERVAL_SECONDS = 300  # 5 minutes between Polls
+
 
 async def poll(session, stream_engine, api_settings, kafka_settings, tracer) -> int:
     """Fetch all Flights from the Schiphol API and publish a Snapshot for each to Kafka.
@@ -93,10 +96,23 @@ async def start():
         }
     )
 
-    total_flights = await poll(session, stream_engine, api_settings, kafka_settings, tracer)
-    logger.info(f"Published {total_flights} flights to Kafka topic '{kafka_settings.topic}'")
-
-    await stream_engine.stop()
+    try:
+        while True:
+            with tracer.start_as_current_span("poll_cycle") as span:
+                try:
+                    total_flights = await poll(
+                        session, stream_engine, api_settings, kafka_settings, tracer
+                    )
+                    span.set_attribute("flights.published", total_flights)
+                    logger.info(
+                        f"Published {total_flights} flights to Kafka topic '{kafka_settings.topic}'"
+                    )
+                except Exception:
+                    span.set_attribute("flights.published", 0)
+                    logger.exception("Poll failed — will retry after %ds", POLL_INTERVAL_SECONDS)
+            await asyncio.sleep(POLL_INTERVAL_SECONDS)
+    finally:
+        await stream_engine.stop()
 
 
 async def shutdown(loop):