feat(stream): bubble footer with timestamp and inline favorite/download

Match the Figma 4206-6509 card layout for /browse: every bubble now
renders a bottom row with the publish timestamp on the left and the
action buttons on the right. Image, album, video, text and link cards
show only the FavoriteButton; file-document cards show the
FavoriteButton plus a new BubbleAttachmentDownloadButton sized to
match. Removes the absolute-positioned favorite from the default
variant, drops the right-aligned timestamp block, and strips the inline
per-row download button from FileDocBubble's default variant since the
download now lives in the footer. The 'latest' masonry variant is
untouched so the home page continues to use LatestFileCard's existing
internal footer.

src/components/messageStream/MessageBubble.tsx

@@ -9,6 +9,7 @@ import { VideoBubble } from "./bubbles/VideoBubble";
 import { LinkPreviewCard } from "./LinkPreviewCard";
 import { formatDateTime } from "./utils/formatTime";
 import { FavoriteButton } from "../../favorites/FavoriteButton";
+import { BubbleAttachmentDownloadButton } from "./BubbleAttachmentDownloadButton";
 
 export type MessageBubbleVariant = "default" | "latest";
 
@@ -47,7 +48,9 @@ export function MessageBubble({
     Bubble === VideoBubble ||
     Bubble === ImageBubble ||
     Bubble === ImageWithTextBubble;
-  const isLatestFileCard = variant === "latest" && Bubble === FileDocBubble;
+  const isFileBubble = Bubble === FileDocBubble;
+  const isLatestVariant = variant === "latest";
+  const isLatestFileCard = isLatestVariant && isFileBubble;
 
   return (
     <div
@@ -63,22 +66,47 @@ export function MessageBubble({
           isVisual || isLatestFileCard ? "p-0" : "px-4 py-3"
         }`}
       >
-        {!isLatestFileCard ? (
+        {isLatestVariant && !isFileBubble ? (
           <FavoriteButton
             resourceId={post.id}
             size="sm"
-            className={`absolute z-20 shadow-lg shadow-black/30 ${
-              variant === "latest" ? "bottom-4 right-4" : "right-3 top-3"
-            }`}
+            className="absolute z-20 bottom-4 right-4 shadow-lg shadow-black/30"
           />
         ) : null}
+
         <Bubble post={post} variant={variant} />
+
         {post.linkPreview ? (
           <div className={isVisual ? "px-4 pt-3" : "mt-3"}>
             <LinkPreviewCard preview={post.linkPreview} />
           </div>
         ) : null}
-        {!isLatestFileCard ? (
+
+        {!isLatestVariant ? (
+          <div
+            className={`flex items-center justify-between gap-3 ${
+              isVisual ? "px-4 pb-3 pt-3" : "mt-3"
+            }`}
+          >
+            <time
+              dateTime={post.publishedAt}
+              className="min-w-0 truncate text-[12px] leading-[19px] text-[#A8A9AE]"
+            >
+              {formatDateTime(post.publishedAt)}
+            </time>
+            <div className="flex shrink-0 items-center gap-2">
+              <FavoriteButton resourceId={post.id} size="sm" />
+              {isFileBubble && post.attachments[0] ? (
+                <BubbleAttachmentDownloadButton
+                  postId={post.id}
+                  attachment={post.attachments[0]}
+                />
+              ) : null}
+            </div>
+          </div>
+        ) : null}
+
+        {isLatestVariant && !isFileBubble ? (
           <time
             dateTime={post.publishedAt}
             className={`block text-right text-[12px] leading-[19px] text-[#A8A9AE] ${