feat: float the player bar above the page

web/src/app/style.css

@@ -36,7 +36,7 @@
   :root[data-performance='low'] button { transition: opacity 160ms; }
 }
 
-.app-shell { height: calc(var(--vh, 1vh) * 100); height: 100dvh; display: grid; grid-template-columns: minmax(0, 1fr); grid-template-rows: minmax(0, 1fr) 104px; overflow: hidden; padding-top: env(safe-area-inset-top); padding-bottom: env(safe-area-inset-bottom); background: var(--color-frame); }
+.app-shell { height: calc(var(--vh, 1vh) * 100); height: 100dvh; display: grid; grid-template-columns: minmax(0, 1fr); grid-template-rows: minmax(0, 1fr) auto; overflow: hidden; padding-top: env(safe-area-inset-top); padding-bottom: env(safe-area-inset-bottom); background: var(--color-frame); }
 .workspace { grid-column: 1; grid-row: 1; display: flex; flex-direction: column; min-height: 0; min-width: 0; }
 .app-shell > .player-bar { grid-column: 1; grid-row: 2; }
 .workspace-header { position: relative; z-index: 30; height: 76px; flex-shrink: 0; display: flex; align-items: center; justify-content: space-between; gap: 20px; padding: 0 24px; background: var(--color-frame); color: var(--color-foreground); border: 0; border-radius: 0; }
@@ -127,6 +127,9 @@
 @media (max-width: 1100px) {
   :root { --detail-panel-width: 420px; }
 }
+@media (min-width: 768px) {
+  .app-shell > .player-bar { justify-self: center; margin-bottom: 12px; }
+}
 /* 通知相对窗口居中，侧栏打开时移到内容区中间，否则会盖住侧栏。窗口太窄时内容区放不下通知，留在原位。 */
 @media (min-width: 1024px) {
   body:has(.detail-panel:not(.detail-panel-closing)) .notifications { left: calc(50% - (var(--detail-panel-width) + 8px) / 2); }

web/src/features/playback/playback.css

@@ -21,6 +21,11 @@
 .player-panel-toggle { color: var(--color-foreground-subtle); }
 .player-panel-toggle:hover:not(:disabled), .player-panel-toggle:focus-visible:not(:disabled), .player-panel-toggle[aria-pressed='true'] { color: var(--color-brand); background: transparent; }
 .player-panel-toggle:active:not(:disabled) { color: var(--color-brand); background: transparent; transform: none; }
+/* 播放栏在布局里占一行，不压在页面上，所以各页面不用留出底部空间。 */
+@media (min-width: 768px) {
+  .player-bar { --color-hover: var(--color-surface-hover); width: min(920px, calc(100% - 16px)); padding: 10px 14px; border-radius: 16px; background: var(--color-panel); box-shadow: 0 8px 24px var(--color-shadow); }
+  .player-artwork .artwork { width: 56px; background: var(--color-surface); }
+}
 @media (max-width: 1100px) {
   .player-bar { gap: 12px; }
   .player-tools .volume-control { margin-right: 4px; }