feat(frontend): replace emoji with inline Material Symbols icon system

Add a self-contained icon system: vendored Material Symbols registry, an
<Icon> component that references a single <symbol> sprite via <use>, plus
IconButton/IconSprite. Replace every emoji/Unicode glyph (logo, theme
switcher, cover placeholder, like/comment counts, lightbox controls, back
links) and add leading icons to key controls. Decorative icons are
aria-hidden; icon-only buttons get labels; theme toggles expose
aria-pressed; counters get accessible names.

Recorded in openspec change material-icons-ui (all tasks complete).

frontend/src/routes/albums/[id]/settings/+page.svelte

@@ -2,6 +2,7 @@
 	import { page } from '$app/stores';
 	import { goto } from '$app/navigation';
 	import { api } from '$lib/api';
+	import Icon from '$lib/components/Icon.svelte';
 	import type { Album, ShareLink } from '$lib/types';
 
 	const albumId = $derived($page.params.id);
@@ -81,7 +82,10 @@
 
 <div class="mb-6 flex items-center justify-between">
 	<h1 class="text-2xl font-bold">Настройки</h1>
-	<a href="/albums/{albumId}" class="text-primary text-sm">← К альбому</a>
+	<a href="/albums/{albumId}" class="text-primary inline-flex items-center gap-1 text-sm">
+		<Icon name="arrow_back" class="size-4" />
+		К альбому
+	</a>
 </div>
 
 {#if error}<p class="text-danger mb-4 text-sm">{error}</p>{/if}
@@ -103,7 +107,13 @@
 			class="border-border bg-bg text-text w-full rounded-lg border px-3 py-2"
 		></textarea>
 	</label>
-	<button class="bg-primary text-primary-fg rounded-lg px-4 py-2 text-sm" type="submit">Сохранить</button>
+	<button
+		class="bg-primary text-primary-fg inline-flex items-center gap-1.5 rounded-lg px-4 py-2 text-sm"
+		type="submit"
+	>
+		<Icon name="save" class="size-4" />
+		Сохранить
+	</button>
 	{#if saved}<span class="text-success ml-3 text-sm">Сохранено</span>{/if}
 </form>
 
@@ -117,9 +127,13 @@
 				class="border-border bg-bg text-text w-32 rounded-lg border px-2 py-1.5"
 			/>
 		</label>
-		<button class="bg-primary text-primary-fg rounded-lg px-4 py-2 text-sm" type="submit"
-			>Создать ссылку</button
+		<button
+			class="bg-primary text-primary-fg inline-flex items-center gap-1.5 rounded-lg px-4 py-2 text-sm"
+			type="submit"
 		>
+			<Icon name="add_link" class="size-4" />
+			Создать ссылку
+		</button>
 	</form>
 	<ul class="divide-border divide-y">
 		{#each shareLinks as link (link.id)}
@@ -129,7 +143,14 @@
 					· <a class="text-primary" href="/share/{link.token}">/share/{link.token}</a>
 				</span>
 				{#if !link.revoked_at}
-					<button type="button" class="text-danger" onclick={() => revoke(link.id)}>Отозвать</button>
+					<button
+						type="button"
+						class="text-danger inline-flex shrink-0 items-center gap-1"
+						onclick={() => revoke(link.id)}
+					>
+						<Icon name="link_off" class="size-4" />
+						Отозвать
+					</button>
 				{/if}
 			</li>
 		{/each}
@@ -138,6 +159,10 @@
 
 <button
 	type="button"
-	class="border-danger text-danger rounded-lg border px-4 py-2 text-sm"
-	onclick={removeAlbum}>Удалить альбом</button
+	class="border-danger text-danger inline-flex items-center gap-1.5 rounded-lg border px-4 py-2 text-sm"
+	onclick={removeAlbum}
 >
+	<Icon name="delete_forever" class="size-4" />
+	Удалить альбом
+</button>
+