web-player: final sweep and guardrails

Add scripts/check-tokens.mjs (npm run lint:tokens, wired into lint) as
a guardrail: fails if src/**/*.svelte reintroduces arbitrary values
outside the B.4 allowlist, factory rounded-*, h-N w-N pairs (should
be size-N), quarter-step fractional spacing, or literal hex/rgba()
colors.

Cleans up the repo until the script reports 0 violations: ~40 h-N w-N
pairs -> size-N (mostly icons, via a one-off script), ~26 quarter-step
fractional spacings rounded to the nearest integer (delta <=1px, e.g.
py-2.75->py-3, gap-1.75->gap-2), stray factory radii (rounded-sm/lg,
bare rounded) migrated to the matching tokens, and two
tracking-[-0.02em] that matched the existing tracking-display token
exactly but had never been migrated. Removes the
stroke-thin/regular/bold recipes (added earlier, zero consumers) —
decision made, not blocking: strokeWidth={n} (13 values, across
almost every component) isn't migrated to CSS because there's no way
to verify without Docker that lucide-svelte honors stroke-width by
class instead of the prop, and a regression there would be silent
across the whole app; the script documents this gap explicitly
instead of pretending full coverage.

Orphan detector: 0 components with no importers. Removes
docs/design-system-refactor-plan.md (earlier plan, superseded by
frontend-refactor-plan.md). web-player/CLAUDE.md gains a "Styles"
section with the B.4 allowlist and the base components to reuse.
Recalculates the baseline table (A.4) and logs it: 61->47 components,
44->11 arbitrary values (the remaining 11 on the allowlist), 13->8
distinct radii, 0 lint:tokens violations.

Verified with npm run check (0 errors), npm run lint:tokens (0
violations) and npm run build. Smoke-tested /login with no console
errors attributable to this change.

web-player/src/lib/components/player/Queue.svelte

@@ -29,7 +29,7 @@
 		</div>
 
 		{#if player.current.id}
-			<p class="mb-2.75 text-eyebrow text-fg-3">Reproduciendo</p>
+			<p class="mb-3 text-eyebrow text-fg-3">Reproduciendo</p>
 			<div class="mb-6 rounded-control bg-accent-tint p-2.5">
 				<MediaIdentity
 					trackId={player.current.id}
@@ -41,7 +41,7 @@
 			</div>
 		{/if}
 
-		<div class="mb-2.75 flex items-center justify-between gap-3">
+		<div class="mb-3 flex items-center justify-between gap-3">
 			<span class="min-w-0 flex-1 truncate text-eyebrow text-fg-3"> A continuación </span>
 			{#if upcoming.length > 0}
 				<button
@@ -64,7 +64,7 @@
 					subtitle={track.artist || '—'}
 					subtitleHref={track.ownerUserId}
 					trackId={track.id}
-					class="p-2.25"
+					class="p-2"
 				>
 					{#snippet trailing()}
 						{#if track.duration}