feat(todo): places are watched by a quiet service, and asked to notify (ADR 0033, D32)

The first walk showed two faults. Android gives a proximity alert of an
app in the background a fix every 30 minutes (17:04:38, then 17:34:43 on
the Pixel), so a short stop goes unseen. And the place did remind, at
17:36:43, but nothing had asked to notify, so Android showed nothing.

A foreground service of the type location now takes its own fixes while
places wait, under the quietest notification there is: as long as
reaching the nearest circle takes at 30 m/s, doubled while the phone
lies still, between 30 s and 5 min. A place with a reminder asks to
notify as any reminder does.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

docs/adr/0033-halkyon-todo.md

@@ -629,18 +629,33 @@ The developer's review of 4 Nov 2026, again beside Todoist's screens.
     and a pin button with the name or a count do the same by hand. The task sheet has a
     Where box, each place with its ⋮; a task's row shows the name and how many more.
   - *Reminders* are on the device, Android alone (`LocationReminderGateway`, a no-op
-    elsewhere, which offers none), as the instance reads no task: the system's
-    `LocationManager.addProximityAlert`, 150 m, no Google services, which GrapheneOS
-    lacks. Planned from the open tasks as `ReminderScheduler` plans reminders
+    elsewhere, which offers none), as the instance reads no task, with no Google
+    services, which GrapheneOS lacks: a foreground service of the type `location`
+    (`LocationWatchService`) takes its own fixes while places wait, stopped as none
+    does. Planned from the open tasks as `ReminderScheduler` plans reminders
     (`planLocationWatches`), cancelled in `TodoPerson.dispose`, kept in the app's private
-    preferences (titles unsealed there, as reminders' are; `allowBackup` is off),
-    registered anew after a restart or an update and on the process's first plan, as a
-    force stop drops them unseen. Fused-provider geofencing was refused: it is Google's.
+    preferences (titles unsealed there, as reminders' are; `allowBackup` is off), and
+    started anew after a restart or an update and as the app opens. Android may refuse
+    the start with the app out of sight, a task synced in; then it starts at the next
+    opening.
+  - *Why a service* (the developer's, 5 Nov 2026, on the first walk): the system's
+    `LocationManager.addProximityAlert`, built first, needs neither service nor
+    notification, but Android gives an app in the background a fix for it every 30
+    minutes (seen on the Pixel: 17:04:38, 17:34:43), so a short stop goes unseen, and
+    asking for updates in the background is held likewise. Keeping it was the
+    alternative, up to half an hour late; fused-provider geofencing was refused, it is
+    Google's. The price is a notification while places wait, on a channel of the least
+    importance (`places_watched`), and the fixes, kept few (`LocationDwell.interval`):
+    as long as reaching the nearest circle takes at 30 m/s, doubled for each fix the
+    phone lay still (moved under 50 m), between 30 s and 5 min, at balanced accuracy on
+    the fused provider of Android's own, GPS before Android 12. What it costs a day
+    wants measuring. A fix rougher than 100 m says nothing of a circle.
   - *Dwell*, so that driving past an EDEKA on the way to the next doesn't remind (the
-    developer's question): crossing the circle schedules a check two minutes later, a
-    crossing back cancels it, and the check notifies only if the phone is still on that
-    side (`LocationDwell`, pure, with JUnit tests CI doesn't run yet), by a fix at most
-    90 s old where there is one, else by the system's last event. A red light of over
+    developer's question): crossing the circle (in at 150 m, out beyond 200 m, so a fix's error
+    doesn't flap) schedules a check two minutes later, a crossing back cancels it, and
+    the check notifies only if the phone is still on that side (`LocationDwell`, pure,
+    with JUnit tests CI doesn't run yet), by a fix at most 90 s old where there is one,
+    else by the last crossing. A red light of over
     two minutes beside the shop still reminds; that is accepted for now.
   - *Once*: a task reminds once until it changes (title, day, places: `stamp`), and an
     alternative that reminded stops the task's others. The notification goes on the
@@ -648,6 +663,8 @@ The developer's review of 4 Nov 2026, again beside Todoist's screens.
   - *Permission*: the position first, then, told why, *Allow all the time* in the
     system's settings, asked as a person chooses such a reminder and never by planning
     (a task may sync in); Settings' Reminders says while it is off, with Turn on, as D31.
+    Notifications are asked for as for any reminder (D31), which the first walk found
+    missing: the place reminded on time and Android showed nothing.
   - *A debug build installs beside the release* (`.debug`, *Todo Debug*), the keys
     differing; SimpleLogin's way back keeps the scheme the instance allows, so with both
     installed Android asks which app answers it. Debug builds log to