Update check: S-22 "Check for update" always asks the server (D-140)

UpdateRepository.checkNow() (default: check(), for throttle-free fakes) skips
the 6-hour throttle of the automatic check (AC-16.2) and restarts its window;
AboutViewModel calls it. Debug builds still never check (AC-16.5).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TQd3pEP9UeN2uifbHknQ7B

android/core/fakes/src/main/kotlin/se/hagstedt/kvitt/fakes/FakeSettingsRepositories.kt

@@ -277,7 +277,8 @@ class FakeSyncRepository(private val store: FakeStore) : SyncRepository {
 
 /**
  * The update state comes from the scenario; `check` and `install` leave it unchanged (debug builds never update,
- * AC-16.5). `check` reports the scenario's state: `Available` as found, anything else as up to date.
+ * AC-16.5). `check` (and `checkNow`, which has no throttle to skip here) reports the scenario's state: `Available` as
+ * found, anything else as up to date.
  */
 class FakeUpdateRepository(private val store: FakeStore) : UpdateRepository {
     override val state: Flow<UpdateState> = store.derive { it.update }