merge: integrate origin/main into feat/improve-rating-ux

Resolve conflicts in RandomAlbums (keep mix rating filter with batch ZIP/offline
selection from upstream) and Settings (SeekbarPreview + mix filter constants).

src/styles/components.css

@@ -496,6 +496,76 @@
   background: var(--accent);
 }
 
+/* ── Album card selection ── */
+.album-card--selectable {
+  cursor: pointer;
+}
+
+.album-card--selected {
+  outline: 2px solid var(--accent);
+  outline-offset: -2px;
+}
+
+.album-card-select-check {
+  position: absolute;
+  top: 6px;
+  left: 6px;
+  width: 22px;
+  height: 22px;
+  border-radius: var(--radius-sm);
+  border: 2px solid rgba(255,255,255,0.7);
+  background: rgba(0,0,0,0.35);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  z-index: 3;
+  pointer-events: none;
+}
+
+.album-card-select-check--on {
+  background: var(--accent);
+  border-color: var(--accent);
+  color: var(--ctp-crust);
+}
+
+/* ── Albums selection bar (portal) ── */
+.albums-selection-bar {
+  position: fixed;
+  bottom: calc(var(--player-height) + 12px);
+  left: 50%;
+  transform: translateX(-50%);
+  z-index: 9000;
+  display: flex;
+  align-items: center;
+  gap: 0.75rem;
+  background: var(--bg-card);
+  border: 1px solid var(--border-subtle);
+  border-radius: var(--radius-lg);
+  padding: 8px 14px;
+  box-shadow: var(--shadow-lg);
+  white-space: nowrap;
+}
+
+.albums-selection-count {
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-primary);
+  padding-right: 4px;
+  border-right: 1px solid var(--border-subtle);
+}
+
+.albums-selection-actions {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+}
+
+.albums-selection-action-btn {
+  display: flex;
+  align-items: center;
+  gap: 5px;
+  font-size: 12px;
+}
 
 .album-card-info {
   padding: var(--space-3) var(--space-4) var(--space-4);