fix: 연차 저장 및 계산 로직 수정

- calculateUsedAnnualLeave()에서 Seoul 타임존 명시
- FragmentSettingsLab 토스트를 커스텀 토스트로 변경
- 연차 저장 시 남은 연차 자동 계산 로직 개선

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

app/src/main/java/com/example/shiftalarm/ShiftRepository.kt

@@ -58,24 +58,24 @@ class ShiftRepository(private val context: Context) {
         dao.clearCustomAlarms()
     }
 
-    // Annual Leave
-    suspend fun calculateUsedAnnualLeave(): Float = withContext(Dispatchers.IO) {
-        val currentYear = java.time.Year.now().toString()
-        val overrides = dao.getAllOverrides()
-        
-        var usedDays = 0f
-        
-        for (override in overrides) {
-            if (override.date.startsWith(currentYear)) {
-                when (override.shift) {
-                    "연차" -> usedDays += 1f
-                    "반년" -> usedDays += 0.5f
-                }
-            }
-        }
-        
-        usedDays
-    }
+ // Annual Leave
+ suspend fun calculateUsedAnnualLeave(): Float = withContext(Dispatchers.IO) {
+ val currentYear = java.time.Year.now(java.time.ZoneId.of("Asia/Seoul")).toString()
+ val overrides = dao.getAllOverrides()
+
+ var usedDays = 0f
+
+ for (override in overrides) {
+ if (override.date.startsWith(currentYear)) {
+ when (override.shift) {
+ "연차" -> usedDays += 1f
+ "반년" -> usedDays += 0.5f
+ }
+ }
+ }
+
+ usedDays
+ }
 
     suspend fun getAnnualLeave(): AnnualLeave? = withContext(Dispatchers.IO) {
         dao.getAnnualLeave()