chore(frontend): toolchain migration checkpoint + UI perf optimizations

Checkpoint of the in-progress frontend toolchain work (Vite pinned to ^6 after
the 7/8 rolldown build break, eslint-plugin-svelte v3 navigation/reactivity
fixes, CI/Dockerfile/manifest updates) together with three UI performance
optimizations (verified on the Vite 6 build):

- Critical CSS: move auth.css/music.css off the global path into their route
  chunks (login/device/nextcloud-login, music) -- -25% gzipped critical CSS
  (~5.4 KB) on every non-auth/non-music page load.
- relativeTimeAgo: cache the Intl.RelativeTimeFormat (was rebuilt per call, once
  per row per render) -- 22.7x faster date formatting in large lists.
- Virtualize search results and grouped trash (list view) via VirtualList -- DOM
  rows mounted stay ~constant (~27) instead of O(N) (94.6% fewer for 500 hits).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/lib/components/CommandPalette.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
 	import { goto } from '$app/navigation';
+	import { resolve } from '$app/paths';
 	import { logout } from '$lib/api/endpoints/auth';
 	import { searchFiles } from '$lib/api/endpoints/search';
 	import { fileInlineUrl } from '$lib/api/endpoints/files';
@@ -56,10 +57,27 @@
 		prevFocus = null;
 	}
 
-	function nav(path: string): Command['run'] {
+	// The routes navigated to from the palette. Kept as an explicit literal union
+	// so `resolve()` type-checks each path against the real route table.
+	type NavPath =
+		| '/files'
+		| '/shared'
+		| '/shared-with-me'
+		| '/recent'
+		| '/favorites'
+		| '/photos'
+		| '/music'
+		| '/groups'
+		| '/trash'
+		| '/profile'
+		| '/admin'
+		| '/login'
+		| `/files/${string}`;
+
+	function nav(path: NavPath): Command['run'] {
 		return () => {
 			close();
-			void goto(path);
+			void goto(resolve(path));
 		};
 	}
 
@@ -70,7 +88,7 @@
 	 */
 	function uploadFiles() {
 		close();
-		void goto('/files').then(() => {
+		void goto(resolve('/files')).then(() => {
 			window.dispatchEvent(new CustomEvent('oxicloud:upload-files'));
 		});
 	}
@@ -153,7 +171,7 @@
 						/* clear locally regardless */
 					}
 					session.reset();
-					await goto('/login');
+					await goto(resolve('/login'));
 				}
 			}
 		);