feat: paginate list views, fix stale page titles, tidy admin filter bar

Bundle of small UI/UX fixes plus a build hygiene tweak.

* List pagination — Home (`/`) and `/authors/[id]` silently capped at
  the backend default of 50 with no UI to advance. New reusable
  `Pager.svelte` (Prev/Next + numbered with ellipsis), URL-synced
  `?page=N`, and filter/search/sort reset to page 1 so users aren't
  stranded on an out-of-range page. Count label now shows a range
  ("Showing 51–100 of 237").

* Stale page title — Pages without a `<svelte:head><title>` left the
  document title at whatever the last manga / author / collection page
  set it to. Move static-route titles into a route-id → title map in
  the root layout and invert every dynamic title to brand-first
  (`Mangalord | {X}`) for consistency.

* Admin filter bar — `/admin/mangas` search input had `flex: 1` and
  ballooned across the row, shoving the sync-state select + Search
  button to the far right. Cap at 24rem, vertical-align the row, and
  promote the previously aria-only "Sync state" label to visible text.

* Build hygiene — `backend/target` had grown to 68 GiB. Cleaned and
  added `[profile.dev] debug = "line-tables-only"` (and `[profile.test]`
  too) to cut future dev builds by ~50–70% while keeping line numbers
  in backtraces.

Also: configure vitest to resolve Svelte's browser entry so
`@testing-library/svelte` can mount components in jsdom — needed for
the new `Pager.svelte.test.ts`.

Bump 0.48.0 -> 0.49.1.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/routes/authors/[id]/+page.ts

@@ -5,13 +5,27 @@ import type { PageLoad } from './$types';
 
 export const ssr = false;
 
-export const load: PageLoad = async ({ params }) => {
+const PAGE_SIZE = 50;
+
+export const load: PageLoad = async ({ params, url }) => {
+    const pageParam = Number(url.searchParams.get('page') ?? '1');
+    const currentPage =
+        Number.isFinite(pageParam) && pageParam >= 1 ? Math.floor(pageParam) : 1;
     try {
         const [author, mangas] = await Promise.all([
             getAuthor(params.id),
-            listAuthorMangas(params.id, { limit: 50 })
+            listAuthorMangas(params.id, {
+                limit: PAGE_SIZE,
+                offset: (currentPage - 1) * PAGE_SIZE
+            })
         ]);
-        return { author, mangas: mangas.items, total: mangas.page.total };
+        return {
+            author,
+            mangas: mangas.items,
+            total: mangas.page.total,
+            currentPage,
+            pageSize: PAGE_SIZE
+        };
     } catch (e) {
         // 404 surfaces as a real SvelteKit error so the framework shell
         // renders the standard not-found page instead of the route's