fix(settings): resolve category drag-and-drop snapping back to original position

Three chained bugs caused dragged categories to snap back immediately on
release, with no order persisted across screen reopens.

Bug 1 — LaunchedEffect fired at the wrong moment (SettingsScreen.kt):
isDragging was listed as a LaunchedEffect key, so releasing the drag
triggered the effect immediately. At that point categories still held
the stale order (DataStore hadn't responded yet), resetting orderedCategories
to the old list and producing the visible snap-back on every drag release.
Fix: remove isDragging from the key list; keep it only as an internal guard.

Bug 2 — reorderFromIds() was a silent no-op (CategoryRepository.kt):
The method body was empty — left as a stub. SettingsViewModel wrapped it
in a db.withTransaction that wrote nothing, so DataStore was never updated
and the custom order was lost on any recomposition.
Fix: call preferences.setCategoryOrder(orderedIds) directly in
updateCategoryOrder(), removing the pointless db transaction wrapper.

Bug 3 — SettingsViewModel.categories ignored DataStore order (SettingsViewModel.kt):
The categories StateFlow was built from observeAll() alone (Room ORDER BY
nombre ASC), always returning alphabetical order regardless of any saved
custom order. VaultViewModel already had the correct pattern but it was
never replicated here.
Fix: mirror VaultViewModel — combine(observeAll, categoryOrderFlow) and
apply applyCategoryOrder() to respect the persisted DataStore order.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: D4vRAM369

app/src/main/java/com/d4vram/threadsvault/ui/settings/SettingsScreen.kt

@@ -123,7 +123,7 @@ fun SettingsScreen(
     val scope = rememberCoroutineScope()
     var showHowToUse by remember { mutableStateOf(false) }
 
-    LaunchedEffect(categories, isDragging) {
+    LaunchedEffect(categories) {
         if (!isDragging) {
             orderedCategories = categories
         }

app/src/main/java/com/d4vram/threadsvault/ui/settings/SettingsViewModel.kt

@@ -20,8 +20,10 @@ import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asSharedFlow
+import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.stateIn
+import com.d4vram.threadsvault.utils.applyCategoryOrder
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 import kotlinx.coroutines.sync.Mutex
@@ -51,8 +53,12 @@ class SettingsViewModel(context: Context) : ViewModel() {
     val autoBackupIntervalHours: StateFlow<Int> = preferences.autoBackupIntervalHoursFlow
         .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), 24)
 
-    val categories: StateFlow<List<CategoryEntity>> = categoryRepository.observeAll()
-        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), emptyList())
+    val categories: StateFlow<List<CategoryEntity>> = combine(
+        categoryRepository.observeAll(),
+        preferences.categoryOrderFlow
+    ) { cats, orderedIds ->
+        applyCategoryOrder(cats, orderedIds)
+    }.stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), emptyList())
 
     private val _saveDocumentEvents = MutableSharedFlow<SaveDocumentRequest>()
     val saveDocumentEvents = _saveDocumentEvents.asSharedFlow()
@@ -300,9 +306,7 @@ class SettingsViewModel(context: Context) : ViewModel() {
     fun updateCategoryOrder(orderedIds: List<Long>) {
         viewModelScope.launch {
             reorderMutex.withLock {
-                db.withTransaction {
-                    categoryRepository.reorderFromIds(orderedIds)
-                }
+                preferences.setCategoryOrder(orderedIds)
             }
         }
     }