feat: add /last-alarm endpoint

Saves the last fired alarm (hour, minute, label, timestamp) to
SharedPreferences when an alarm fires. New GET /last-alarm endpoint
returns the last alarm info or 404 if none has fired yet.

app/src/main/java/com/example/helios_alarm_clock/service/AlarmRingService.kt

@@ -22,6 +22,7 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.cancel
 import kotlinx.coroutines.launch
+import java.util.Calendar
 import javax.inject.Inject
 
 @AndroidEntryPoint
@@ -55,13 +56,17 @@ class AlarmRingService : Service() {
 
         startSound()
 
-        // Delete the fired alarm from the database
+        // Save as last alarm and delete from the database
         if (alarmId.isNotEmpty()) {
             scope.launch {
                 try {
+                    val alarm = alarmDao.getById(alarmId)
+                    if (alarm != null) {
+                        saveLastAlarm(alarm.hour, alarm.minute, alarm.label)
+                    }
                     alarmDao.deleteById(alarmId)
                 } catch (e: Exception) {
-                    Log.e(TAG, "Failed to delete alarm $alarmId", e)
+                    Log.e(TAG, "Failed to process alarm $alarmId", e)
                 }
             }
         }
@@ -142,6 +147,17 @@ class AlarmRingService : Service() {
             .build()
     }
 
+    private fun saveLastAlarm(hour: Int, minute: Int, label: String) {
+        val prefs = getSharedPreferences("last_alarm", Context.MODE_PRIVATE)
+        val now = Calendar.getInstance()
+        prefs.edit()
+            .putInt("hour", hour)
+            .putInt("minute", minute)
+            .putString("label", label)
+            .putLong("firedAt", now.timeInMillis)
+            .apply()
+    }
+
     companion object {
         private const val TAG = "AlarmRingService"
         const val NOTIFICATION_ID = 2

app/src/main/java/com/example/helios_alarm_clock/service/KtorService.kt

@@ -181,6 +181,29 @@ class KtorService : Service() {
                     val alarms = alarmDao.getAll()
                     call.respond(alarms)
                 }
+
+                get("/last-alarm") {
+                    val prefs = this@KtorService.getSharedPreferences(
+                        "last_alarm",
+                        Context.MODE_PRIVATE
+                    )
+                    val firedAt = prefs.getLong("firedAt", -1)
+                    if (firedAt == -1L) {
+                        call.respond(
+                            HttpStatusCode.NotFound,
+                            ErrorResponse("No alarm has fired yet")
+                        )
+                    } else {
+                        call.respond(
+                            LastAlarmResponse(
+                                hour = prefs.getInt("hour", 0),
+                                minute = prefs.getInt("minute", 0),
+                                label = prefs.getString("label", "") ?: "",
+                                firedAt = firedAt
+                            )
+                        )
+                    }
+                }
             }
         }.also { it.start(wait = false) }
     }
@@ -231,3 +254,6 @@ data class StatusResponse(val status: String)
 
 @Serializable
 data class ErrorResponse(val error: String)
+
+@Serializable
+data class LastAlarmResponse(val hour: Int, val minute: Int, val label: String, val firedAt: Long)