all_channels: Make row item at least 44px tall

Add SizedBox(height: 40, width: 52), the size of the toggle, as a
placeholder for hidden toggle to prevent UI jump. Adjust Row padding
(top: 2, bottom: 2) to maintain 44px touch target.

Author: chungwwei

lib/widgets/all_channels.dart

@@ -104,7 +104,7 @@ class AllChannelsListEntry extends StatelessWidget {
           narrow: ChannelNarrow(channel.streamId))),
       onLongPress: () => showChannelActionSheet(context, channelId: channel.streamId),
       child: Padding(
-        padding: EdgeInsetsDirectional.only(start: 8, end: 12),
+        padding: const EdgeInsets.fromLTRB(8, 2, 12, 2),
         child: Row(spacing: 6, children: [
           Icon(
             size: 20,
@@ -120,7 +120,7 @@ class AllChannelsListEntry extends StatelessWidget {
                 height: 20 / 17,
               ).merge(weightVariableTextStyle(context, wght: 600)),
               channel.name)),
-          if (hasContentAccess) _SubscribeToggle(channel: channel),
+          hasContentAccess ? _SubscribeToggle(channel: channel) : const SizedBox(height: 40, width: 52)
         ])));
   }
 }

test/widgets/all_channels_test.dart

@@ -203,6 +203,9 @@ void main() {
       } else {
         check(maybeToggle).isNull();
       }
+
+      final touchTargetSize = tester.getSize(findElement);
+      check(touchTargetSize.height).equals(44);
     }
   });