wrongmove: stabilise setup_periodic_tasks tests after market-aggregator add

CI test-unit failed on pipeline #49 because the three TestSetupPeriodicTasks
cases asserted exact call counts on `sender.add_periodic_task` and the
new unconditional `daily-market-aggregator` registration bumped each by
one. Fix:

- `tasks/listing_tasks.py`: lifted the market-aggregator registration
  out of the SchedulesConfig try-block — it's now independent of the
  user's SCRAPE_SCHEDULES (a malformed scrape config no longer takes
  the aggregator down with it).
- `tests/unit/test_listing_tasks.py`: updated the four cases to account
  for the +1 unconditional aggregator call. `test_handles_config_error_
  gracefully` now asserts the aggregator still registers when
  SchedulesConfig.from_env raises (regression coverage for the
  independence guarantee).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tasks/listing_tasks.py

@@ -635,27 +635,33 @@ async def _dump_listings_full_inner(
 
 @app.on_after_finalize.connect
 def setup_periodic_tasks(sender, **kwargs):
-    """Register periodic tasks from environment configuration."""
+    """Register periodic tasks from environment configuration.
+
+    The daily market aggregator is registered unconditionally so it stays
+    healthy even when the user's `SCRAPE_SCHEDULES` env var is malformed —
+    the two systems are orthogonal.
+    """
     try:
-        config = SchedulesConfig.from_env()
+        config: SchedulesConfig | None = SchedulesConfig.from_env()
     except ValueError as e:
         celery_logger.error(f"Failed to load schedule configuration: {e}")
-        return
+        config = None
 
-    for schedule in config.get_enabled_schedules():
-        celery_logger.info(
-            f"Registering periodic task: {schedule.name} at {schedule.hour}:{schedule.minute}"
-        )
+    if config is not None:
+        for schedule in config.get_enabled_schedules():
+            celery_logger.info(
+                f"Registering periodic task: {schedule.name} at {schedule.hour}:{schedule.minute}"
+            )
 
-        sender.add_periodic_task(
-            crontab(
-                minute=schedule.minute,
-                hour=schedule.hour,
-                day_of_week=schedule.day_of_week,
-            ),
-            dump_listings_task.s(schedule.to_query_parameters().model_dump_json()),
-            name=schedule.name,
-        )
+            sender.add_periodic_task(
+                crontab(
+                    minute=schedule.minute,
+                    hour=schedule.hour,
+                    day_of_week=schedule.day_of_week,
+                ),
+                dump_listings_task.s(schedule.to_query_parameters().model_dump_json()),
+                name=schedule.name,
+            )
 
     # Daily market aggregator — fires after the 03:00 RENT scrape so the
     # snapshot reflects today's freshly-pulled data. Imported lazily to