feat(frontend): fullscreen toggle and album back button

- add fullscreen/fullscreen_exit icons and a top-bar toggle (right of themes)
- add back arrow left of the album title to return to the albums overview

frontend/src/lib/components/AppShell.svelte

@@ -24,13 +24,29 @@
 	let railWidth = $state(RAIL.def);
 	let panelWidth = $state(PANEL.def);
 
+	let isFullscreen = $state(false);
+
 	onMount(() => {
 		const r = parseInt(localStorage.getItem(RAIL.key) ?? '', 10);
 		if (r >= RAIL.min && r <= RAIL.max) railWidth = r;
 		const p = parseInt(localStorage.getItem(PANEL.key) ?? '', 10);
 		if (p >= PANEL.min && p <= PANEL.max) panelWidth = p;
+
+		const onFs = () => (isFullscreen = !!document.fullscreenElement);
+		document.addEventListener('fullscreenchange', onFs);
+		onFs();
+		return () => document.removeEventListener('fullscreenchange', onFs);
 	});
 
+	async function toggleFullscreen() {
+		try {
+			if (document.fullscreenElement) await document.exitFullscreen();
+			else await document.documentElement.requestFullscreen();
+		} catch {
+			/* недоступно */
+		}
+	}
+
 	function startResize(side: 'left' | 'right', ev: PointerEvent) {
 		ev.preventDefault();
 		const cfg = side === 'left' ? RAIL : PANEL;
@@ -134,6 +150,16 @@
 				</a>
 			{/if}
 			<ThemeSwitcher />
+			<button
+				type="button"
+				class="text-text-muted hover:bg-bg-muted hover:text-text inline-flex items-center justify-center rounded-md p-1.5"
+				aria-label={isFullscreen ? 'Выйти из полноэкранного режима' : 'На весь экран'}
+				title={isFullscreen ? 'Выйти из полноэкранного режима' : 'На весь экран'}
+				aria-pressed={isFullscreen}
+				onclick={toggleFullscreen}
+			>
+				<Icon name={isFullscreen ? 'fullscreen_exit' : 'fullscreen'} />
+			</button>
 		</div>
 	</header>
 

frontend/src/lib/icons/registry.ts

@@ -43,7 +43,9 @@ export const icons = {
 	check: { path: '<path fill="currentColor" d="m9.55 18l-5.7-5.7l1.425-1.425L9.55 15.15l9.175-9.175L20.15 7.4z"/>' },
 	menu: { path: '<path fill="currentColor" d="M3 18v-2h18v2zm0-5v-2h18v2zm0-5V6h18v2z"/>' },
 	grid_view: { path: '<path fill="currentColor" d="M3 3v8h8V3zm10 0v8h8V3zM3 13v8h8v-8zm10 0v8h8v-8z"/>' },
-	wallpaper: { path: '<path fill="currentColor" d="M4 4h7V2H4c-1.1 0-2 .9-2 2v7h2zm6 9l-4 5h12l-3-4l-2.03 2.71zm7-4.5c0-.83-.67-1.5-1.5-1.5S14 7.67 14 8.5s.67 1.5 1.5 1.5S17 9.33 17 8.5M20 2h-7v2h7v7h2V4c0-1.1-.9-2-2-2m0 18h-7v2h7c1.1 0 2-.9 2-2v-7h-2zM4 13H2v7c0 1.1.9 2 2 2h7v-2H4z"/>' }
+	wallpaper: { path: '<path fill="currentColor" d="M4 4h7V2H4c-1.1 0-2 .9-2 2v7h2zm6 9l-4 5h12l-3-4l-2.03 2.71zm7-4.5c0-.83-.67-1.5-1.5-1.5S14 7.67 14 8.5s.67 1.5 1.5 1.5S17 9.33 17 8.5M20 2h-7v2h7v7h2V4c0-1.1-.9-2-2-2m0 18h-7v2h7c1.1 0 2-.9 2-2v-7h-2zM4 13H2v7c0 1.1.9 2 2 2h7v-2H4z"/>' },
+	fullscreen: { path: '<path fill="currentColor" d="M7 14H5v5h5v-2H7zm-2-4h2V7h3V5H5zm12 7h-3v2h5v-5h-2zM14 5v2h3v3h2V5z"/>' },
+	fullscreen_exit: { path: '<path fill="currentColor" d="M5 16h3v3h2v-5H5zm3-8H5v2h5V5H8zm6 11h2v-3h3v-2h-5zm2-11v3h-2v2h5V5z"/>' }
 } satisfies Record<string, IconDef>;
 
 export type IconName = keyof typeof icons;

frontend/src/routes/(app)/albums/[id]/+page.svelte

@@ -155,7 +155,17 @@
 		<div
 			class="border-border bg-chrome sticky top-0 z-10 flex items-center justify-between gap-3 border-b px-3 py-2"
 		>
+			<div class="flex min-w-0 items-center gap-1">
+				<a
+					href="/"
+					class="text-text-muted hover:bg-bg-muted hover:text-text inline-flex shrink-0 items-center justify-center rounded-md p-1.5"
+					aria-label="Ко всем альбомам"
+					title="Ко всем альбомам"
+				>
+					<Icon name="arrow_back" class="size-5" />
+				</a>
 				<h1 class="text-text truncate text-sm font-medium">{album?.title ?? ''}</h1>
+			</div>
 			<div class="flex items-center gap-3">
 				<DensityControl />
 				{#if canUpload}