Make dark mode more colorful and give chrome bars a full tint

Mirror the earlier light-mode pastel/colorful pass for dark mode:
boost tc()'s lightness and chroma, and richen --mf-bg/--mf-elevated/
--mf-panel-bg/--mf-bar-bg/--mf-hairline the same way, so dark mode
reads as colorful instead of near-grayscale.

Sidebar, Queue, and MobileHeader used bg-bg directly, so in dark mode
they stayed almost black regardless of hue. Add --mf-chrome-bg (an
alias to --mf-bg in light mode, a solid color-mix of --mf-hero-tint
into --mf-bg in dark mode) and switch those three to bg-chrome, so
they read as a full, solid colored bar in dark mode instead of a
fading gradient (per feedback: a whole bar, not a gradient).

Also fixes glass-bar (PlayerBar/TabsBar): it set
`background-image: var(--mf-bar-bg)`, but --mf-bar-bg is a plain
color, not a valid <image>, so the declaration was silently dropped
and these bars never actually showed their tint in either mode. Changed
to background-color.

web-player/src/routes/layout.css

@@ -5,6 +5,7 @@
 	--font-display: 'Sora Variable', ui-sans-serif, system-ui, sans-serif;
 
 	--color-bg: var(--mf-bg);
+	--color-chrome: var(--mf-chrome-bg);
 	--color-elevated: var(--mf-elevated);
 	--color-surface: var(--mf-surface);
 	--color-surface-2: var(--mf-surface-2);
@@ -127,7 +128,7 @@
 	transition-duration: var(--default-transition-duration);
 }
 @utility glass-bar {
-	background-image: var(--mf-bar-bg);
+	background-color: var(--mf-bar-bg);
 	border-top: 1px solid var(--mf-hairline);
 	backdrop-filter: blur(24px);
 }