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/lib/components/Pager.svelte

@@ -0,0 +1,128 @@
+<script lang="ts">
+    type Props = {
+        page: number;
+        totalPages: number;
+        onChange: (page: number) => void;
+        testid?: string;
+    };
+
+    let { page, totalPages, onChange, testid }: Props = $props();
+
+    type Slot = number | 'ellipsis';
+
+    // Compact layout: always show first + last, surround the current page with
+    // its direct neighbours, and use "…" to elide the rest. Keeps the bar to
+    // at most 7 buttons regardless of totalPages.
+    function buildSlots(p: number, total: number): Slot[] {
+        if (total <= 7) {
+            return Array.from({ length: total }, (_, i) => i + 1);
+        }
+        const out: Slot[] = [1];
+        if (p <= 4) {
+            for (let i = 2; i <= 5; i++) out.push(i);
+            out.push('ellipsis');
+            out.push(total);
+        } else if (p >= total - 3) {
+            out.push('ellipsis');
+            for (let i = total - 4; i <= total; i++) out.push(i);
+        } else {
+            out.push('ellipsis');
+            out.push(p - 1);
+            out.push(p);
+            out.push(p + 1);
+            out.push('ellipsis');
+            out.push(total);
+        }
+        return out;
+    }
+
+    const slots = $derived(buildSlots(page, totalPages));
+</script>
+
+{#if totalPages > 1}
+    <nav class="pager" aria-label="Pagination" data-testid={testid}>
+        <button
+            type="button"
+            class="step"
+            disabled={page <= 1}
+            onclick={() => onChange(page - 1)}
+            aria-label="Previous page"
+        >
+            ‹ Prev
+        </button>
+
+        {#each slots as slot, i (i)}
+            {#if slot === 'ellipsis'}
+                <span class="ellipsis" aria-hidden="true">…</span>
+            {:else}
+                <button
+                    type="button"
+                    class="num"
+                    class:active={slot === page}
+                    aria-current={slot === page ? 'page' : undefined}
+                    aria-label={`Go to page ${slot}`}
+                    onclick={() => onChange(slot)}
+                >
+                    {slot}
+                </button>
+            {/if}
+        {/each}
+
+        <button
+            type="button"
+            class="step"
+            disabled={page >= totalPages}
+            onclick={() => onChange(page + 1)}
+            aria-label="Next page"
+        >
+            Next ›
+        </button>
+    </nav>
+{/if}
+
+<style>
+    .pager {
+        display: flex;
+        flex-wrap: wrap;
+        align-items: center;
+        gap: var(--space-1);
+        margin: var(--space-4) 0;
+        justify-content: center;
+    }
+
+    .step,
+    .num {
+        min-width: 36px;
+        height: 36px;
+        padding: 0 var(--space-2);
+        background: var(--surface);
+        border: 1px solid var(--border);
+        border-radius: var(--radius-md);
+        color: var(--text);
+        cursor: pointer;
+        font-size: var(--font-sm);
+    }
+
+    .step:hover:not(:disabled),
+    .num:hover:not(.active) {
+        border-color: var(--primary);
+    }
+
+    .step:disabled {
+        opacity: 0.4;
+        cursor: not-allowed;
+    }
+
+    .num.active {
+        background: var(--primary);
+        color: var(--primary-contrast);
+        border-color: var(--primary);
+        cursor: default;
+    }
+
+    .ellipsis {
+        padding: 0 var(--space-1);
+        color: var(--text-muted);
+        user-select: none;
+    }
+</style>