fix(video): keep scroll position and stop pause from going fullscreen

- VideoBubble: stopPropagation on the inline <video> element so
  clicks on the native controls (play/pause/seek) don't bubble up
  to the outer tile, which previously promoted any control click
  into a fullscreen overlay.
- VideoPlayer: replace overflow:hidden body lock with the iOS-safe
  position-fixed + scroll-restore pattern. Closing the fullscreen
  player now returns the page to the exact scroll offset it had,
  instead of snapping back to the top on iOS Safari.

src/components/messageStream/bubbles/VideoBubble.tsx

@@ -87,6 +87,7 @@ function VideoAttachmentCard({
             controls
             playsInline
             autoPlay
+            onClick={(e) => e.stopPropagation()}
             className="absolute inset-0 h-full w-full"
           />
           <AttachmentDownloadPill

src/components/messageStream/overlays/VideoPlayer.tsx

@@ -70,11 +70,36 @@ function PlayerView({
       if (e.key === "Escape") onClose();
     };
     window.addEventListener("keydown", onKey);
-    const prevOverflow = document.body.style.overflow;
-    document.body.style.overflow = "hidden";
+
+    // iOS-compatible scroll lock: pin the body in place at the current scroll
+    // offset, then restore both styles and scroll position on cleanup. Plain
+    // `overflow: hidden` doesn't work on iOS Safari and can reset scroll to 0.
+    const scrollY = window.scrollY;
+    const body = document.body;
+    const prev = {
+      position: body.style.position,
+      top: body.style.top,
+      left: body.style.left,
+      right: body.style.right,
+      width: body.style.width,
+      overflow: body.style.overflow,
+    };
+    body.style.position = "fixed";
+    body.style.top = `-${scrollY}px`;
+    body.style.left = "0";
+    body.style.right = "0";
+    body.style.width = "100%";
+    body.style.overflow = "hidden";
+
     return () => {
       window.removeEventListener("keydown", onKey);
-      document.body.style.overflow = prevOverflow;
+      body.style.position = prev.position;
+      body.style.top = prev.top;
+      body.style.left = prev.left;
+      body.style.right = prev.right;
+      body.style.width = prev.width;
+      body.style.overflow = prev.overflow;
+      window.scrollTo(0, scrollY);
     };
   }, [onClose]);