Stop URl preview from covering message box (#29215)

* Stop URl preview from covering message box

Fixes #23874 by adding a bit of padding.

1em should be sufficient to prevent the browser's URl preview from covering the entry box.

* test: update timeline screenshots

* test: update test, fewer messages are displayed

---------

Co-authored-by: Florian Duros <[email protected]>
Co-authored-by: Florian D <[email protected]>

playwright/e2e/read-receipts/new-messages-thread-roots.spec.ts

@@ -57,8 +57,8 @@ test.describe("Read receipts", { tag: "@mergequeue" }, () => {
                 await util.openThread("ThreadRoot");
 
                 // Then the thread root is marked as read in the main timeline,
-                // 30 remaining messages are unread - 7 messages are displayed under the thread root
-                await util.assertUnread(room2, 30 - 7);
+                // 30 remaining messages are unread - 6 messages are displayed under the thread root
+                await util.assertUnread(room2, 30 - 6);
             });
 
             test("Creating a new thread based on a reply makes the room unread", async ({

res/css/structures/_RoomView.pcss

@@ -35,6 +35,7 @@ Please see LICENSE files in the repository root for full details.
         width: 100%;
         flex: 0 0 auto;
         margin-right: 2px;
+        padding-bottom: 1em;
     }
 }