feat(data): ui preferences, the real ticker and its binding

The ticker is injected rather than read from the composition so the shell's
per-second text can be driven by a test scheduler instead of a wall clock.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wmy1BpCKi8KeSjaWhYuCPV

app/src/main/java/de/jeanlucmakiola/clockula/data/di/TimeModule.kt

@@ -5,11 +5,13 @@ import dagger.Module
 import dagger.hilt.InstallIn
 import dagger.hilt.components.SingletonComponent
 import de.jeanlucmakiola.clockula.data.time.AndroidBootIdProvider
+import de.jeanlucmakiola.clockula.data.time.RealTicker
 import de.jeanlucmakiola.clockula.data.time.SystemElapsedRealtimeClock
 import de.jeanlucmakiola.clockula.data.time.SystemWallClock
 import de.jeanlucmakiola.clockula.data.time.SystemZoneProvider
 import de.jeanlucmakiola.clockula.domain.time.BootIdProvider
 import de.jeanlucmakiola.clockula.domain.time.ElapsedRealtimeClock
+import de.jeanlucmakiola.clockula.domain.time.Ticker
 import de.jeanlucmakiola.clockula.domain.time.WallClock
 import de.jeanlucmakiola.clockula.domain.time.ZoneProvider
 
@@ -34,4 +36,7 @@ abstract class TimeModule {
 
     @Binds
     abstract fun bindBootIdProvider(impl: AndroidBootIdProvider): BootIdProvider
+
+    @Binds
+    abstract fun bindTicker(impl: RealTicker): Ticker
 }

app/src/main/java/de/jeanlucmakiola/clockula/data/prefs/SettingsPrefs.kt

@@ -92,4 +92,16 @@ class SettingsPrefs @Inject constructor(private val store: PrefStore) {
     suspend fun setTimerDuration(duration: Duration) = store.set(ClockPrefs.timerDurationMillis, duration)
 
     suspend fun setHomeZoneId(zoneId: String?) = store.set(ClockPrefs.homeZoneId, zoneId)
+
+    // --- first-launch bookkeeping (M4) ---
+
+    /**
+     * Whether the POST_NOTIFICATIONS request has already been shown once.
+     * Distinct-until-changed through [PrefStore.flow], so writing an unrelated
+     * preference does not re-emit it.
+     */
+    val notificationPermissionAsked: Flow<Boolean> = store.flow(UiPrefs.notificationPermissionAsked)
+
+    suspend fun markNotificationPermissionAsked() =
+        store.set(UiPrefs.notificationPermissionAsked, true)
 }

app/src/main/java/de/jeanlucmakiola/clockula/data/prefs/UiPrefs.kt

@@ -0,0 +1,11 @@
+package de.jeanlucmakiola.clockula.data.prefs
+
+import de.jeanlucmakiola.floret.prefs.Pref
+import de.jeanlucmakiola.floret.prefs.booleanPref
+
+/** The shell's own on-disk keys — first-launch bookkeeping, not a user setting. */
+object UiPrefs {
+    /** Whether the POST_NOTIFICATIONS request has been shown once. */
+    val notificationPermissionAsked: Pref<Boolean> =
+        booleanPref("notification_permission_asked", false)
+}

app/src/main/java/de/jeanlucmakiola/clockula/data/time/RealTicker.kt

@@ -0,0 +1,27 @@
+package de.jeanlucmakiola.clockula.data.time
+
+import de.jeanlucmakiola.clockula.domain.time.Ticker
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flow
+import kotlin.time.Duration
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/** The [Ticker] seam over `delay`: emit, then wait [ticks]' period, forever. */
+@Singleton
+class RealTicker @Inject constructor() : Ticker {
+
+    /**
+     * Cold, and per-collector: two readouts on different cadences get two
+     * independent streams, and a collector that walks away takes its own
+     * `delay` with it. The first emission is immediate, so a subscriber is
+     * never blank for a period.
+     */
+    override fun ticks(period: Duration): Flow<Unit> = flow {
+        while (true) {
+            emit(Unit)
+            delay(period)
+        }
+    }
+}