fix(android): guard setExactAndAllowWhileIdle with canScheduleExactAlarms() check

SecurityException crash on Android 12+ when SCHEDULE_EXACT_ALARM special
access not user-granted. Now checks canScheduleExactAlarms() and falls back
to setAndAllowWhileIdle() (inexact, no special permission needed). Both
schedule() and cancel() wrapped in try/catch to prevent future alarm crashes.

frontend/android/app/src/main/kotlin/com/teamsb/tis_rms/AlarmScheduler.kt

@@ -4,6 +4,7 @@ import android.app.AlarmManager
 import android.app.PendingIntent
 import android.content.Context
 import android.content.Intent
+import android.os.Build
 import android.os.SystemClock
 import android.util.Log
 
@@ -13,21 +14,39 @@ object AlarmScheduler {
     private const val INTERVAL_MS = 2 * 60 * 1000L // 2 minutes
 
     fun schedule(context: Context) {
-        val alarmManager = context.getSystemService(Context.ALARM_SERVICE) as AlarmManager
-        val pi = buildPendingIntent(context)
-        alarmManager.cancel(pi)
-        alarmManager.setExactAndAllowWhileIdle(
-            AlarmManager.ELAPSED_REALTIME_WAKEUP,
-            SystemClock.elapsedRealtime() + INTERVAL_MS,
-            pi
-        )
-        Log.d(TAG, "scheduled: next check in ${INTERVAL_MS / 1000}s")
+        try {
+            val alarmManager = context.getSystemService(Context.ALARM_SERVICE) as AlarmManager
+            val pi = buildPendingIntent(context)
+            alarmManager.cancel(pi)
+            val triggerAt = SystemClock.elapsedRealtime() + INTERVAL_MS
+
+            val canExact = Build.VERSION.SDK_INT < Build.VERSION_CODES.S ||
+                    alarmManager.canScheduleExactAlarms()
+
+            if (canExact) {
+                alarmManager.setExactAndAllowWhileIdle(
+                    AlarmManager.ELAPSED_REALTIME_WAKEUP, triggerAt, pi
+                )
+                Log.d(TAG, "scheduled (exact): next check in ${INTERVAL_MS / 1000}s")
+            } else {
+                alarmManager.setAndAllowWhileIdle(
+                    AlarmManager.ELAPSED_REALTIME_WAKEUP, triggerAt, pi
+                )
+                Log.d(TAG, "scheduled (inexact): next check in ${INTERVAL_MS / 1000}s")
+            }
+        } catch (e: Exception) {
+            Log.e(TAG, "schedule failed: ${e.message}")
+        }
     }
 
     fun cancel(context: Context) {
-        val alarmManager = context.getSystemService(Context.ALARM_SERVICE) as AlarmManager
-        alarmManager.cancel(buildPendingIntent(context))
-        Log.d(TAG, "cancelled")
+        try {
+            val alarmManager = context.getSystemService(Context.ALARM_SERVICE) as AlarmManager
+            alarmManager.cancel(buildPendingIntent(context))
+            Log.d(TAG, "cancelled")
+        } catch (e: Exception) {
+            Log.e(TAG, "cancel failed: ${e.message}")
+        }
     }
 
     private fun buildPendingIntent(context: Context): PendingIntent {