feat(appointment): auto-expire unpaid bookings via Symfony Scheduler

Run the 15-min payment-expiry every minute through Symfony Scheduler so
unpaid pending bookings flip to expired without a system crontab. Install
symfony/scheduler; extract the expiry logic into AppointmentExpiryService
(reused by the existing command); add ExpireAppointmentsMessage + handler
and an #[AsSchedule] provider (RecurringMessage::every 1 minute); wire a
scheduler_default transport in messenger.yaml. Slots already free
just-in-time via isSlotTaken, so this only syncs the DB status.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

symfony.lock

@@ -183,6 +183,18 @@
             "config/routes.yaml"
         ]
     },
+    "symfony/scheduler": {
+        "version": "7.4",
+        "recipe": {
+            "repo": "github.com/symfony/recipes",
+            "branch": "main",
+            "version": "7.2",
+            "ref": "caea3c928ee9e1b21288fd76aef36f16ea355515"
+        },
+        "files": [
+            "src/Schedule.php"
+        ]
+    },
     "symfony/security-bundle": {
         "version": "7.4",
         "recipe": {