fix(frontend): paint video poster frames, clip round videos to circle

frontend/src/lib/components/MediaVersionThumb.svelte

@@ -4,6 +4,7 @@
   import type { MediaVersion } from "$lib/api/types";
   import Icon from "$lib/components/ui/Icon.svelte";
   import Spinner from "$lib/components/ui/Spinner.svelte";
+  import { poster } from "$lib/media/poster";
 
   interface Props {
     version: MediaVersion;
@@ -37,7 +38,13 @@
     </a>
   {:else if result.state === "ready" && vk === "video"}
     <a href={result.url} target="_blank" rel="noopener">
-      <video src={result.url} muted preload="metadata"></video>
+      <video
+        src={result.url}
+        muted
+        playsinline
+        preload="metadata"
+        use:poster
+      ></video>
       <span class="play"><Icon name="large-play" size="1.5rem" /></span>
     </a>
   {:else if result.state === "ready"}