Dedupe native transfer/notification code and split ServerProvider into focused controllers

Consolidates duplicated GET/PUT/notification-channel logic across
DownloadService/ShareUploadService/SyncEngine into shared Kotlin helpers,
gives upload/download real batch queueing instead of dropping a second
concurrent batch, and dedupes repeated Dart channel-argument boilerplate.

Replaces the 2300+ line ServerProvider god object with ten focused
ChangeNotifiers (SessionController, SettingsController, FilesController,
PhotosController, FavoritesController, TrashController, SharesController,
RecentController, SyncStatusController, PickController) plus ItemOperations,
a plain coordinator for cross-domain item mutations - fixing the coupling
where device-sync status, per-tab data, and global UI prefs all lived in
one object. Updates every view/widget call site accordingly and refreshes
the architecture/server/standards/styling docs to match.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lib/providers/photos_controller.dart

@@ -0,0 +1,190 @@
+import 'dart:async';
+import 'package:flutter/material.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+import '../models/nextcloud_item.dart';
+import 'files_controller.dart';
+import 'session_controller.dart';
+
+/// The Photos tab: every image/video across the whole account (not just
+/// the currently browsed folder - see [fetchAllMedia]). Depends on
+/// [FilesController] only for the shared [StorageScope] toggle and
+/// [FilesController.applyCommonFilters] - Photos' own favorites-only/
+/// hidden toggles are independent of Files', but the storage-scope split
+/// (cloud vs external) is one shared setting across every tab.
+class PhotosController extends ChangeNotifier {
+  final SessionController session;
+  final FilesController files;
+
+  static const _prefShowFavoritesOnlyPhotos = 'ui_show_favorites_only_photos';
+  static const _prefShowHiddenPhotos = 'ui_show_hidden_photos';
+  static const _prefSortField = 'ui_sort_field';
+  static const _prefSortAscending = 'ui_sort_ascending';
+
+  List<NextcloudItem> _allMedia = [];
+  bool _isLoading = false;
+  String? _errorMessage;
+
+  bool _showFavoritesOnly = false;
+  bool _showHidden = false;
+  FileSortField _sortField = FileSortField.name;
+  bool _sortAscending = true;
+
+  PhotosController(this.session, this.files) {
+    session.addAccountClearedListener(_onAccountCleared);
+    session.addAccountActivatedListener(_onAccountActivated);
+  }
+
+  bool get isLoading => _isLoading;
+  String? get errorMessage => _errorMessage;
+  bool get showFavoritesOnly => _showFavoritesOnly;
+  bool get showHidden => _showHidden;
+  FileSortField get sortField => _sortField;
+  bool get sortAscending => _sortAscending;
+
+  /// All images/videos across the whole account (not just the currently
+  /// browsed folder) — see [fetchAllMedia].
+  List<NextcloudItem> get items {
+    final media = _allMedia.where((i) => i.isMedia).toList();
+    final filtered = files.applyCommonFilters(
+      media,
+      showFavoritesOnly: _showFavoritesOnly,
+      showHidden: _showHidden,
+    )..sort((a, b) => _compare(a, b));
+    return _sortAscending ? filtered : filtered.reversed.toList();
+  }
+
+  int _compare(NextcloudItem a, NextcloudItem b) {
+    switch (_sortField) {
+      case FileSortField.name:
+        return a.name.toLowerCase().compareTo(b.name.toLowerCase());
+      case FileSortField.dateCreated:
+        return a.dateCreated.compareTo(b.dateCreated);
+      case FileSortField.dateModified:
+        return a.lastModified.compareTo(b.lastModified);
+      case FileSortField.size:
+        return a.size.compareTo(b.size);
+    }
+  }
+
+  void _onAccountCleared() {
+    _allMedia = [];
+    _isLoading = false;
+    _errorMessage = null;
+    notifyListeners();
+  }
+
+  Future<void> _onAccountActivated() async {
+    final id = session.activeAccountId;
+    if (id != null) {
+      final prefs = await session.prefsFuture;
+      String k(String base) => session.accountStore.accountPrefKey(id, base);
+      _showFavoritesOnly =
+          prefs.getBool(k(_prefShowFavoritesOnlyPhotos)) ?? false;
+      _showHidden = prefs.getBool(k(_prefShowHiddenPhotos)) ?? false;
+      final sortFieldName = prefs.getString(k(_prefSortField));
+      _sortField = FileSortField.values.firstWhere(
+        (f) => f.name == sortFieldName,
+        orElse: () => FileSortField.name,
+      );
+      _sortAscending = prefs.getBool(k(_prefSortAscending)) ?? true;
+      notifyListeners();
+    }
+    unawaited(fetchAllMedia());
+  }
+
+  /// Loads every image/video across the whole account for the Photos tab.
+  Future<void> fetchAllMedia() async {
+    final service = session.service;
+    if (!session.isLoggedIn || service == null) return;
+    final gen = session.sessionGeneration;
+
+    _isLoading = true;
+    _errorMessage = null;
+    notifyListeners();
+
+    try {
+      final media = await service.fetchAllMedia();
+      if (gen != session.sessionGeneration) return;
+      _allMedia = media;
+      debugPrint('[PhotosController] Loaded ${_allMedia.length} media items');
+    } catch (e) {
+      if (gen != session.sessionGeneration) return;
+      debugPrint('[PhotosController] Error fetching all media: $e');
+      _errorMessage = e.toString().replaceAll('Exception: ', '');
+    } finally {
+      if (gen == session.sessionGeneration) {
+        _isLoading = false;
+        notifyListeners();
+      }
+    }
+  }
+
+  void _persistAccountPref(
+    String baseKey,
+    void Function(SharedPreferences prefs, String key) write,
+  ) {
+    final id = session.activeAccountId;
+    if (id == null) return;
+    session.prefsFuture.then(
+      (p) => write(p, session.accountStore.accountPrefKey(id, baseKey)),
+    );
+  }
+
+  void toggleFavoritesFilter() {
+    _showFavoritesOnly = !_showFavoritesOnly;
+    notifyListeners();
+    _persistAccountPref(
+      _prefShowFavoritesOnlyPhotos,
+      (p, key) => p.setBool(key, _showFavoritesOnly),
+    );
+  }
+
+  Future<void> toggleShowHidden() async {
+    if (!_showHidden) {
+      if (!await session.passGate(
+        session.lockHiddenFiles,
+        'Unlock to show hidden files',
+      )) {
+        return;
+      }
+    }
+    _showHidden = !_showHidden;
+    notifyListeners();
+    _persistAccountPref(
+      _prefShowHiddenPhotos,
+      (p, key) => p.setBool(key, _showHidden),
+    );
+  }
+
+  void setSortField(FileSortField field) {
+    if (_sortField == field) return;
+    _sortField = field;
+    notifyListeners();
+    _persistAccountPref(_prefSortField, (p, key) => p.setString(key, field.name));
+  }
+
+  void toggleSortOrder() {
+    _sortAscending = !_sortAscending;
+    notifyListeners();
+    _persistAccountPref(
+      _prefSortAscending,
+      (p, key) => p.setBool(key, _sortAscending),
+    );
+  }
+
+  /// Removes an item by path (a delete elsewhere in the app) - called by
+  /// `ItemOperations.deleteItem` after a successful server call.
+  void applyDelete(String path) {
+    _allMedia = _allMedia.where((i) => i.path != path).toList();
+    notifyListeners();
+  }
+
+  /// Patches a favorite-toggle result into [items]' source list in place -
+  /// called by `ItemOperations.toggleItemFavorite` after a successful
+  /// server call.
+  void applyFavoriteToggle(NextcloudItem updated) {
+    final index = _allMedia.indexWhere((i) => i.id == updated.id);
+    if (index != -1) _allMedia[index] = updated;
+    notifyListeners();
+  }
+}