web-player: TypeScript helpers (partial)

Add src/lib/actions/pressable.ts and clickOutside.ts (Svelte actions;
role/tabindex stay static in markup for SSR accessibility, the action
only adds click + Enter/Space) and src/lib/toggle.svelte.ts
(createToggle), used by playlists.svelte.ts and queuePanel.svelte.ts.

format.ts: adds plural(n, one, many); migrates the repo's 15 manual
pluralizations, unifying them to lowercase (visible diff in
Playlists, Home, liked, Explore).

player.svelte.ts: adds toQueueItem, isQueueCurrent, playAllOrToggle,
playShuffled; renames addToQueue -> playNextItem (the old name was
misleading: it inserts next, not at the end). Migrates the 5 places
that repeated the isCurrentQueue/playAll pattern (album, playlist,
liked, mix, Home). Simplifies liked.svelte.ts and recentlyPlayed.ts
with object spread instead of rebuilding every field by hand.

navigation.svelte.ts: adds searchHref (migrates the duplicated
buildHref from TopBar and Explore) and appNavLinks (added; its
adoption in Sidebar/TabsBar is left for a later pass, as noted
there).

menus.svelte.ts: createTrackMenu() replaces the manual context-menu
state (contextMenu + contextMenuStateFor + addToQueue) in Home,
Explore and Mix.

Deliberately left pending: removing tracks.ts's TrackTarget wrapper
and its 8 accessors is deferred — it's the riskiest change in the
plan, touches types across Home/Explore/Mix/menus, and couldn't be
visually verified without Docker this session.

Verified with npm run check/build.

web-player/src/routes/(app)/albums/[id]/+page.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-	import { player, toQueueItems } from '$lib/player/player.svelte';
+	import { player, toQueueItems, isQueueCurrent, playAllOrToggle } from '$lib/player/player.svelte';
 	import Page from '$lib/components/ui/Page.svelte';
 	import Modal from '$lib/components/ui/Modal.svelte';
 	import Alert from '$lib/components/ui/Alert.svelte';
@@ -19,12 +19,10 @@
 	let editing = $state(false);
 	let confirmingDelete = $state(false);
 
-	const isCurrentQueue = $derived(tracks.some((track) => track.id === player.current.id));
+	const isCurrentQueue = $derived(isQueueCurrent(tracks));
 
 	function playAll() {
-		if (tracks.length === 0) return;
-		if (isCurrentQueue) player.toggle();
-		else player.playQueue(toQueueItems(tracks), 0);
+		playAllOrToggle(toQueueItems(tracks));
 	}
 </script>