feat(core,fuse,gui): "On this day" strip above the photos timeline

Add a PhotosOnThisDay control request, served from the stored timeline:
photos whose local capture date matches today's in earlier years, one
row per group. The GUI shows a card per year ("3 years ago") with the
year's newest photo as its cover; clicking a card scrolls the timeline
to that day. The strip is revealed only at the top of the whole,
unfiltered timeline, so it gives the grid its room back once you
scroll or filter.

crates/pdfs-gui/resources/style.css

@@ -74,6 +74,9 @@ progressbar.browser-status-meter trough, progressbar.browser-status-meter progre
 .photo-video-badge-small { padding: 3px; min-width: 0; min-height: 0; }
 .photo-tile:hover .photo-video-badge { background: color-mix(in srgb, var(--accent-bg-color) 85%, transparent); }
 .photo-group-badge { font-size: 0.68rem; font-weight: 700; letter-spacing: 0.04em; color: white; background: rgba(0, 0, 0, 0.55); border-radius: 6px; padding: 1px 5px; margin: 6px; text-shadow: 0 1px 2px rgba(0, 0, 0, 0.9); }
+.memory-card { padding: 0; border-radius: 12px; }
+.memory-cover { border-radius: 12px; background: alpha(currentColor, 0.06); }
+.memory-label { font-weight: 700; color: white; text-shadow: 0 1px 3px rgba(0, 0, 0, 0.9); padding: 22px 10px 6px 10px; background: linear-gradient(to top, rgba(0, 0, 0, 0.6), rgba(0, 0, 0, 0)); }
 .album-card { padding: 0; border-radius: 16px; transition: background 180ms ease; }
 .album-card:hover { background: alpha(currentColor, 0.07); }
 .album-cover { border-radius: 16px; background: alpha(currentColor, 0.06); box-shadow: 0 4px 16px rgba(0, 0, 0, 0.32); transition: box-shadow 180ms ease; }