feat(core,fuse,gui): push daemon events, polish Photos, adopt newer widgets

The app and the tray stop polling. pdfs-core adds Request::Subscribe: the
connection stays open and carries Event lines (status, transfers, and
Changed with a Topic), with a heartbeat while quiet. In pdfs-fuse, an
EventHub gives each subscriber a mailbox, code that changes something
publishes its topic, and a sampler publishes the status, transfers and sync
progress when they differ. The app follows the feed on one thread, paints
status and transfers as they arrive, and reloads the page on screen when its
topic changes, including after changes made with the pdfs CLI. A hidden
window keeps the changes and catches up when focused. Front-ends fall back
to polling a daemon that predates subscriptions. Refresh buttons leave the
page headers; F5 and Ctrl+R still reload from the server.

Photos gets a scrubber overlaid on the right edge of the timeline in place
of the slider and scrollbar. It shows the years, appears when the pointer
comes near or the timeline scrolls, names the month under the pointer and
jumps to it on drag. Upload becomes a split button whose menu holds the
Google Photos import. Tiles are pooled per row and rebound instead of
rebuilt, hover scales the thumbnail to 1.02 without a shadow, and tiles
lose their tooltip.

On libadwaita 1.8 or newer the app uses AdwSpinner, AdwToggleGroup,
AdwButtonRow and AdwShortcutsDialog, and keeps look-alike stand-ins on
older releases (src/compat.rs, widgets/compat.rs). It still builds against
libadwaita 1.5 and picks at run time, creating the newer widgets by class
name through GtkBuilder, so every package gets them. PDFS_STAND_IN_WIDGETS
forces the stand-ins.

The Sync and share-link icons draw in full again: GTK drops group
transforms from symbolic icons, so their coordinates are baked into the
paths. All catalogs are updated and complete.

crates/pdfs-gui/resources/style.css

@@ -66,19 +66,19 @@ scale.browser-status-meter trough { min-width: 104px; min-height: 6px; }
 .viewer-nav-btn { background-color: rgba(0, 0, 0, 0.45); color: white; margin: 20px; min-width: 44px; min-height: 44px; border-radius: 50%; opacity: 0.7; transition: opacity 150ms ease, background-color 150ms ease; }
 .viewer-nav-btn:hover { background-color: rgba(0, 0, 0, 0.85); color: white; opacity: 1; }
 .viewer-nav-btn:disabled { opacity: 0; }
-.photo-scrubber { min-width: 20px; padding: 0 2px; }
-.photo-scrubber value { font-weight: 600; background-color: var(--popover-bg-color); border-radius: 6px; padding: 2px 8px; }
+.photo-scrubber { background: linear-gradient(to left, alpha(var(--window-bg-color), 0.92) 40%, alpha(var(--window-bg-color), 0)); }
+.photo-scrubber-knob { background-color: var(--accent-bg-color); border-radius: 2px; }
+.photo-scrubber-bubble { font-weight: 600; background-color: var(--popover-bg-color); color: var(--popover-fg-color); border-radius: 999px; padding: 4px 12px; box-shadow: 0 1px 4px rgba(0, 0, 0, 0.3); }
 .viewer-spinner { color: white; }
 .viewer-status { color: white; font-size: 1rem; background-color: rgba(0, 0, 0, 0.75); padding: 12px 24px; border-radius: 12px; }
 .viewer-info-panel { background-color: var(--window-bg-color); border-left: 1px solid alpha(currentColor, 0.12); }
 
 /* Photos grid */
 .gallery-day { font-size: 0.82rem; font-weight: 700; letter-spacing: 0.04em; text-transform: uppercase; color: alpha(currentColor, 0.65); padding: 2px 2px 6px 2px; }
-.photo-tile { padding: 0; margin: 0; min-height: 0; min-width: 0; border: none; border-radius: 4px; background: none; box-shadow: none; transition: box-shadow 180ms ease; }
-.photo-tile:hover { box-shadow: 0 8px 22px rgba(0, 0, 0, 0.45); }
+.photo-tile { padding: 0; margin: 0; min-height: 0; min-width: 0; border: none; border-radius: 4px; background: none; box-shadow: none; }
 .photo-tile:focus { outline: 2px solid var(--accent-color); outline-offset: -2px; }
 .photo-thumb { transition: transform 220ms ease; }
-.photo-tile:hover .photo-thumb { transform: scale(1.06); }
+.photo-tile:hover .photo-thumb { transform: scale(1.02); }
 .photo-check { color: white; background: rgba(0, 0, 0, 0.5); border-radius: 999px; padding: 3px; }
 .photo-check-on { background: var(--accent-bg-color); color: var(--accent-fg-color); }
 .photo-tile-selected { outline: 3px solid var(--accent-bg-color); outline-offset: -3px; }
@@ -97,7 +97,7 @@ scale.browser-status-meter trough { min-width: 104px; min-height: 6px; }
 .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; }
 .album-card:hover .album-cover { box-shadow: 0 10px 26px rgba(0, 0, 0, 0.5); }
 .album-card:hover .photo-thumb { transform: scale(1.05); }
-.view-switch button { padding-left: 18px; padding-right: 18px; }
+.view-switch button, .view-switch toggle { padding-left: 18px; padding-right: 18px; }
 
 /* Shared with Me: what a share lets me do, as a tinted pill beside the name. */
 .role-pill { padding: 2px 10px; border-radius: 999px; font-weight: 600; color: var(--accent-color); background-color: color-mix(in srgb, var(--accent-bg-color) 16%, transparent); }