Fix keyword alarm and add visual indicators

- Fix: Only keyword-matched deals send notifications
- Add: Visual indicator for keyword-matched deals (badge + border)
- Add: Polling interval setting with persistence
- Add: Version check in settings
- Add: Update dialog on app start

app/src/main/java/com/hotdeal/alarm/data/local/preferences/AppSettings.kt

@@ -0,0 +1,40 @@
+package com.hotdeal.alarm.data.local.preferences
+
+import android.content.Context
+import androidx.datastore.core.DataStore
+import androidx.datastore.preferences.core.Preferences
+import androidx.datastore.preferences.core.edit
+import androidx.datastore.preferences.core.intPreferencesKey
+import androidx.datastore.preferences.preferencesDataStore
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.map
+
+/**
+ * 앱 설정 저장 (DataStore)
+ */
+class AppSettings(private val context: Context) {
+    
+    private val Context.dataStore: DataStore<Preferences> by preferencesDataStore(name = "app_settings")
+    
+    companion object {
+        private val POLLING_INTERVAL_KEY = intPreferencesKey("polling_interval_minutes")
+        private const val DEFAULT_INTERVAL = 2
+    }
+    
+    /**
+     * 폴� 주기 (분)
+     */
+    val pollingInterval: Flow<Int> = context.dataStore.data
+        .map { preferences ->
+            preferences[POLLING_INTERVAL_KEY] ?: DEFAULT_INTERVAL
+        }
+    
+    /**
+     * 폴� 주기 설정 저장
+     */
+    suspend fun setPollingInterval(minutes: Int) {
+        context.dataStore.edit { preferences ->
+            preferences[POLLING_INTERVAL_KEY] = minutes
+        }
+    }
+}