refactor(mobile): pages (#9246)

* refactor(mobile): pages

* refactor

* album pages

* pages

* pages

* use *.page.dart

* representation

* put back module

mobile/lib/utils/immich_loading_overlay.dart

@@ -0,0 +1,69 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_hooks/flutter_hooks.dart';
+import 'package:immich_mobile/extensions/build_context_extensions.dart';
+import 'package:immich_mobile/shared/ui/delayed_loading_indicator.dart';
+
+final _loadingEntry = OverlayEntry(
+  builder: (context) => SizedBox.square(
+    dimension: double.infinity,
+    child: DecoratedBox(
+      decoration:
+          BoxDecoration(color: context.colorScheme.surface.withAlpha(200)),
+      child: const Center(
+        child: DelayedLoadingIndicator(
+          delay: Duration(seconds: 1),
+          fadeInDuration: Duration(milliseconds: 400),
+        ),
+      ),
+    ),
+  ),
+);
+
+ValueNotifier<bool> useProcessingOverlay() {
+  return use(const _LoadingOverlay());
+}
+
+class _LoadingOverlay extends Hook<ValueNotifier<bool>> {
+  const _LoadingOverlay();
+
+  @override
+  _LoadingOverlayState createState() => _LoadingOverlayState();
+}
+
+class _LoadingOverlayState
+    extends HookState<ValueNotifier<bool>, _LoadingOverlay> {
+  late final _isLoading = ValueNotifier(false)..addListener(_listener);
+  OverlayEntry? _loadingOverlay;
+
+  void _listener() {
+    setState(() {
+      WidgetsBinding.instance.addPostFrameCallback((_) {
+        if (_isLoading.value) {
+          _loadingOverlay?.remove();
+          _loadingOverlay = _loadingEntry;
+          Overlay.of(context).insert(_loadingEntry);
+        } else {
+          _loadingOverlay?.remove();
+          _loadingOverlay = null;
+        }
+      });
+    });
+  }
+
+  @override
+  ValueNotifier<bool> build(BuildContext context) {
+    return _isLoading;
+  }
+
+  @override
+  void dispose() {
+    _isLoading.dispose();
+    super.dispose();
+  }
+
+  @override
+  Object? get debugValue => _isLoading.value;
+
+  @override
+  String get debugLabel => 'useProcessingOverlay<>';
+}