perf: gate deadline reminder polling (Closes #717)

src/main.py

@@ -106,6 +106,9 @@ async def _push_channel_loop(dispatch, *, interval: float) -> None:
 
 async def _push_poll_loop() -> None:
     interval = max(5.0, float(os.getenv("STACKCHAIN_PUSH_POLL_SECONDS", "30")))
+    deadline_interval = max(
+        60.0, float(os.getenv("STACKCHAIN_DEADLINE_POLL_SECONDS", "600"))
+    )
     send_timeout = max(
         1.0, float(os.getenv("STACKCHAIN_PUSH_SEND_TIMEOUT_SECONDS", "10"))
     )
@@ -145,7 +148,9 @@ async def _push_poll_loop() -> None:
 
     channel_tasks = (
         asyncio.create_task(_push_channel_loop(dispatch_unread, interval=interval)),
-        asyncio.create_task(_push_channel_loop(dispatch_deadlines, interval=interval)),
+        asyncio.create_task(
+            _push_channel_loop(dispatch_deadlines, interval=deadline_interval)
+        ),
     )
     try:
         done, _pending = await asyncio.wait(

src/push_notifications.py

@@ -289,10 +289,23 @@ async def _dispatch_deadline_reminders_unlocked(
     devices = await asyncio.to_thread(store.deadline_reminder_devices)
     if not devices:
         return 0
+    current = now or datetime.now(timezone.utc)
+    eligible_devices = []
+    for device in devices:
+        try:
+            local_now = current.astimezone(ZoneInfo(device.timezone))
+        except ZoneInfoNotFoundError:
+            continue
+        if (
+            local_now.hour >= device.reminder_hour
+            and device.delivered_local_day != local_now.date().isoformat()
+        ):
+            eligible_devices.append(device)
+    if not eligible_devices:
+        return 0
     snapshot = await assigned()
     if snapshot.get("complete") is False:
         return 0
-    current = now or datetime.now(timezone.utc)
     due_cutoff = current + timedelta(hours=48)
     due_count = 0
     for item in snapshot.get("items", []):
@@ -356,6 +369,6 @@ async def _dispatch_deadline_reminders_unlocked(
             return 1
 
     results = await asyncio.gather(
-        *(dispatch_device(device) for device in devices), return_exceptions=True
+        *(dispatch_device(device) for device in eligible_devices), return_exceptions=True
     )
     return sum(result for result in results if isinstance(result, int))