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/lib/player/liked.svelte.ts

@@ -34,13 +34,10 @@ class LikedStore {
 		const items = toQueueItems(tracks);
 		const next: Record<string, LikedTrack> = {};
 		items.forEach((item, i) => {
-			next[String(item.id)] = {
-				id: String(item.id),
-				title: item.title,
-				artist: item.artist,
-				explicit: item.explicit,
-				ownerUserId: item.ownerUserId,
-				listensCount: item.listensCount,
+			const id = String(item.id);
+			next[id] = {
+				...item,
+				id,
 				duration: tracks[i].duration,
 				likedAt: new Date(tracks[i].createdAt).getTime()
 			};
@@ -58,17 +55,7 @@ class LikedStore {
 		const wasLiked = id in before;
 		const next = { ...before };
 		if (wasLiked) delete next[id];
-		else {
-			next[id] = {
-				id,
-				title: track.title,
-				artist: track.artist,
-				explicit: track.explicit,
-				ownerUserId: track.ownerUserId,
-				duration: track.duration,
-				likedAt: Date.now()
-			};
-		}
+		else next[id] = { ...track, id, likedAt: Date.now() };
 		this.entries = next;
 
 		try {