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/+page.svelte

@@ -13,10 +13,13 @@
     import { listTags, type Tag } from '$lib/api/tags';
     import Chip from '$lib/components/Chip.svelte';
     import MangaCard from '$lib/components/MangaCard.svelte';
+    import Pager from '$lib/components/Pager.svelte';
     import Search from '@lucide/svelte/icons/search';
     import SlidersHorizontal from '@lucide/svelte/icons/sliders-horizontal';
     import Plus from '@lucide/svelte/icons/plus';
 
+    const PAGE_SIZE = 50;
+
     let mangas: MangaCardData[] = $state([]);
     let search = $state('');
     let sort: MangaSort = $state('recent');
@@ -36,11 +39,21 @@
     let total: number | null = $state(null);
     let loading = $state(true);
     let error: string | null = $state(null);
+    let currentPage = $state(1);
 
     const activeFilterCount = $derived(
         (statusFilter ? 1 : 0) + selectedGenres.length + selectedTags.length
     );
 
+    const totalPages = $derived(
+        total != null && total > 0 ? Math.ceil(total / PAGE_SIZE) : 1
+    );
+
+    // 1-indexed range like "51–100 of 237", clamped to the actual loaded set
+    // in case the last page is short.
+    const rangeStart = $derived(mangas.length === 0 ? 0 : (currentPage - 1) * PAGE_SIZE + 1);
+    const rangeEnd = $derived((currentPage - 1) * PAGE_SIZE + mangas.length);
+
     async function load() {
         loading = true;
         error = null;
@@ -50,7 +63,9 @@
                 status: statusFilter || undefined,
                 genreIds: selectedGenres.map((g) => g.id),
                 tagIds: selectedTags.map((t) => t.id),
-                sort
+                sort,
+                limit: PAGE_SIZE,
+                offset: (currentPage - 1) * PAGE_SIZE
             });
             mangas = result.items;
             total = result.page.total;
@@ -71,11 +86,29 @@
             params.set('genres', selectedGenres.map((g) => g.id).join(','));
         if (selectedTags.length)
             params.set('tags', selectedTags.map((t) => t.id).join(','));
+        if (currentPage > 1) params.set('page', String(currentPage));
         const qs = params.toString();
         const url = qs ? `/?${qs}` : '/';
         goto(url, { replaceState: true, keepFocus: true, noScroll: true });
     }
 
+    // Filter / search / sort changes invalidate the current page — drop back
+    // to page 1 so the user isn't stranded on an out-of-range page when the
+    // result set shrinks. Direct page navigation calls `goToPage()` instead.
+    function resetAndReload() {
+        currentPage = 1;
+        syncUrl();
+        load();
+    }
+
+    function goToPage(p: number) {
+        if (p === currentPage) return;
+        currentPage = p;
+        syncUrl();
+        load();
+        if (browser) window.scrollTo({ top: 0, behavior: 'smooth' });
+    }
+
     async function hydrateFromUrl() {
         // Parse the query and resolve the supplied ids back to full Tag /
         // Genre objects so the chip rows render real labels.
@@ -100,6 +133,8 @@
             const tags = await listTags({ limit: 50 });
             selectedTags = tags.filter((t) => tagIds.includes(t.id));
         }
+        const pageParam = Number(url.searchParams.get('page') ?? '1');
+        currentPage = Number.isFinite(pageParam) && pageParam >= 1 ? Math.floor(pageParam) : 1;
         // Open the filters panel if anything is active so the user can see why.
         if (statusFilter || selectedGenres.length || selectedTags.length) {
             filtersOpen = true;
@@ -108,32 +143,27 @@
 
     async function onSubmit(e: SubmitEvent) {
         e.preventDefault();
-        syncUrl();
-        await load();
+        resetAndReload();
     }
 
     function onSortChange() {
-        syncUrl();
-        load();
+        resetAndReload();
     }
 
     function onStatusChange() {
-        syncUrl();
-        load();
+        resetAndReload();
     }
 
     function toggleGenre(g: Genre) {
         selectedGenres = selectedGenres.some((x) => x.id === g.id)
             ? selectedGenres.filter((x) => x.id !== g.id)
             : [...selectedGenres, g];
-        syncUrl();
-        load();
+        resetAndReload();
     }
 
     function removeTag(t: Tag) {
         selectedTags = selectedTags.filter((x) => x.id !== t.id);
-        syncUrl();
-        load();
+        resetAndReload();
     }
 
     function pickTag(t: Tag) {
@@ -143,8 +173,7 @@
         tagDraft = '';
         tagSuggestions = [];
         tagSuggestHighlight = -1;
-        syncUrl();
-        load();
+        resetAndReload();
     }
 
     function onTagDraftInput() {
@@ -192,8 +221,7 @@
         statusFilter = '';
         selectedGenres = [];
         selectedTags = [];
-        syncUrl();
-        load();
+        resetAndReload();
     }
 
     onMount(async () => {
@@ -383,7 +411,7 @@
 {:else}
     {#if total !== null}
         <p class="count" data-testid="manga-total">
-            Showing {mangas.length} of {total}
+            Showing {rangeStart}–{rangeEnd} of {total}
         </p>
     {/if}
     <ul class="manga-grid" data-testid="manga-list">
@@ -391,6 +419,12 @@
             <MangaCard manga={m} authors={m.authors} genres={m.genres} />
         {/each}
     </ul>
+    <Pager
+        page={currentPage}
+        {totalPages}
+        onChange={goToPage}
+        testid="manga-pager"
+    />
 {/if}
 
 <style>