feat(mobile): pinch to zoom on asset grid (#2905)

mobile/lib/modules/home/ui/asset_grid/immich_asset_grid.dart

@@ -1,3 +1,6 @@
+import 'dart:math';
+
+import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
@@ -51,6 +54,12 @@ class ImmichAssetGrid extends HookConsumerWidget {
     final enableHeroAnimations = useState(false);
     final transitionDuration = ModalRoute.of(context)?.transitionDuration;
 
+    final perRow = useState(
+      assetsPerRow ?? settings.getSetting(AppSettingsEnum.tilesPerRow)!,
+    );
+    final scaleFactor = useState(7.0 - perRow.value);
+    final baseScaleFactor = useState(7.0 - perRow.value);
+
     useEffect(
       () {
         // Wait for transition to complete, then re-enable
@@ -80,10 +89,30 @@ class ImmichAssetGrid extends HookConsumerWidget {
         onWillPop: onWillPop,
         child: HeroMode(
           enabled: enableHeroAnimations.value,
+          child: RawGestureDetector(
+            gestures: {
+              CustomScaleGestureRecognizer:
+                  GestureRecognizerFactoryWithHandlers<
+                          CustomScaleGestureRecognizer>(
+                      () => CustomScaleGestureRecognizer(),
+                      (CustomScaleGestureRecognizer scale) {
+                scale.onStart = (details) {
+                  baseScaleFactor.value = scaleFactor.value;
+                };
+
+                scale.onUpdate = (details) {
+                  scaleFactor.value =
+                      max(min(5.0, baseScaleFactor.value * details.scale), 1.0);
+                  if (7 - scaleFactor.value.toInt() != perRow.value) {
+                    perRow.value = 7 - scaleFactor.value.toInt();
+                  }
+                };
+                scale.onEnd = (details) {};
+              })
+            },
             child: ImmichAssetGridView(
               onRefresh: onRefresh,
-            assetsPerRow: assetsPerRow ??
+              assetsPerRow: perRow.value,
-                settings.getSetting(AppSettingsEnum.tilesPerRow),
               listener: listener,
               showStorageIndicator: showStorageIndicator ??
                   settings.getSetting(AppSettingsEnum.storageIndicator),
@@ -98,6 +127,7 @@ class ImmichAssetGrid extends HookConsumerWidget {
               visibleItemsListener: visibleItemsListener,
             ),
           ),
+        ),
       );
     }
 
@@ -113,3 +143,11 @@ class ImmichAssetGrid extends HookConsumerWidget {
     );
   }
 }
+
+/// accepts a gesture even though it should reject it (because child won)
+class CustomScaleGestureRecognizer extends ScaleGestureRecognizer {
+  @override
+  void rejectGesture(int pointer) {
+    acceptGesture(pointer);
+  }
+}