fix(download): verify payload freshness before restoring the update state

On restart the update-available state was restored purely from the
saved date. Also compare the installed payload file names against
dated sources, and re-check when they no longer match.

app/src/main/java/com/example/research/ui/settings/SettingsViewModel.kt

@@ -524,6 +524,25 @@ class SettingsViewModel(
     ): List<DictionarySource> =
         DictionarySourceFileMatcher.installedSources(sources, dictionaries)
 
+    private suspend fun installedDictionariesAreCurrent(): Boolean {
+        val sources = preferencesManager.dictionarySources.first()
+        val dictionaries = localDictionaryRepository.dictionaries.first()
+        val datedEnabledSources = installedEnabledSources(sources, dictionaries)
+            .filter { DictionarySource.hasDatePlaceholder(it.urlTemplate) }
+        if (datedEnabledSources.isEmpty()) return true
+        val fileNames = localDictionaryRepository.listDictionaryPayloadFileNames(
+            preferencesManager.dictionaryPath
+        ) ?: return true
+        val today = DateUtils.getCurrentDateString()
+        return datedEnabledSources.all { source ->
+            val baseName = DictionarySource.extractFileName(source.urlTemplate, today)
+                .removeSuffix(".gz")
+                .removeSuffix(".dsl")
+                .removeSuffix(".dz")
+            fileNames.any { it.startsWith(baseName) }
+        }
+    }
+
     private fun cancelDownload() {
         // Cancel the ViewModel-side scan job so no further status recomputes
         localDictionaryRepository.cancelIndexing()
@@ -584,7 +603,10 @@ class SettingsViewModel(
                         "NeedsUpdate" -> DictionaryStatus.NeedsUpdate
                         else -> null
                     }
-                    if (restoredStatus != null && savedStatusDate == DateUtils.getCurrentDateString()) {
+                    if (restoredStatus != null &&
+                        savedStatusDate == DateUtils.getCurrentDateString() &&
+                        withContext(Dispatchers.IO) { installedDictionariesAreCurrent() }
+                    ) {
                         dictionaryStatus.value = restoredStatus
                     } else {
                         dictionaryStatus.value = DictionaryStatus.Checking