feat: /profile dashboard with tabbed preferences, account, bookmarks, collections (0.18.0)

Tabbed user dashboard at `/profile` that absorbs `/settings` and
surfaces bookmarks + collections in one place.

- New `/profile` shell with tabs: Overview (counts), Preferences
  (theme + reader prefs, ported from /settings; works for guests
  via localStorage), Account (password change; auth-gated),
  Bookmarks, Collections. Guest tab list is filtered to what they
  can actually use.
- `/settings` is a 308 redirect to `/profile/preferences` so old
  bookmarks land cleanly. The "Settings" link in the top nav is
  replaced by a Profile link between Upload and Bookmarks; Bookmarks
  + Collections stay as shortcuts per the user spec.
- Extracts `lib/components/BookmarkList.svelte` and
  `lib/components/CollectionsGrid.svelte` so the top-level
  /bookmarks + /collections routes and the new profile tabs render
  the same UI without duplication. Both layers use a three-state
  load (authenticated / guest / error) to handle network hiccups
  inline.
- Deep links preserved via `?next=` on every sign-in CTA.

88 frontend unit tests + svelte-check clean; 12 of 12 e2e tests in
profile.spec.ts and reader-mode.spec.ts pass (8 other e2e failures
predate this branch and stay flagged for cleanup).

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

frontend/src/routes/bookmarks/+page.svelte

@@ -1,6 +1,5 @@
 <script lang="ts">
-    import { fileUrl } from '$lib/api/client';
-    import BookImage from '@lucide/svelte/icons/book-image';
+    import BookmarkList from '$lib/components/BookmarkList.svelte';
 
     let { data } = $props();
     const authenticated = $derived(data.authenticated);
@@ -25,122 +24,10 @@
 {:else if bookmarks.length === 0}
     <p class="hint" data-testid="bookmarks-empty">No bookmarks yet.</p>
 {:else}
-    <ul class="bookmark-list" data-testid="bookmark-list">
-        {#each bookmarks as b (b.id)}
-            <li class="bookmark">
-                <a href="/manga/{b.manga_id}" class="cover-link" aria-hidden="true" tabindex="-1">
-                    {#if b.manga_cover_image_path}
-                        <img
-                            src={fileUrl(b.manga_cover_image_path)}
-                            alt=""
-                            class="cover"
-                            loading="lazy"
-                        />
-                    {:else}
-                        <div class="cover cover-placeholder">
-                            <BookImage size={22} aria-hidden="true" />
-                        </div>
-                    {/if}
-                </a>
-                <div class="meta">
-                    <a
-                        href="/manga/{b.manga_id}"
-                        class="title"
-                        data-testid="bookmark-title"
-                    >
-                        {b.manga_title ?? 'Unknown manga'}
-                    </a>
-                    {#if b.chapter_id && b.chapter_number != null}
-                        <a
-                            href="/manga/{b.manga_id}/chapter/{b.chapter_number}"
-                            class="target"
-                        >
-                            Chapter {b.chapter_number}{#if b.page != null && b.page > 0} — page {b.page}{/if}
-                        </a>
-                    {:else if b.chapter_id}
-                        <!-- Chapter bookmark whose chapter was deleted;
-                             chapter_id != null but chapter_number == null
-                             because the LEFT JOIN found nothing. -->
-                        <span class="target muted">(chapter removed)</span>
-                    {:else}
-                        <span class="target muted">Whole manga</span>
-                    {/if}
-                    <span class="created">
-                        Bookmarked {new Date(b.created_at).toLocaleDateString()}
-                    </span>
-                </div>
-            </li>
-        {/each}
-    </ul>
+    <BookmarkList {bookmarks} />
 {/if}
 
 <style>
-    .bookmark-list {
-        list-style: none;
-        padding: 0;
-        margin: 0;
-    }
-
-    .bookmark {
-        display: grid;
-        grid-template-columns: 64px 1fr;
-        gap: var(--space-4);
-        align-items: start;
-        padding: var(--space-3) 0;
-        border-bottom: 1px solid var(--border);
-    }
-
-    .cover-link {
-        display: block;
-        line-height: 0;
-    }
-
-    .cover {
-        width: 64px;
-        height: 96px;
-        object-fit: cover;
-        border-radius: var(--radius-md);
-        background: var(--surface);
-    }
-
-    .cover-placeholder {
-        display: flex;
-        align-items: center;
-        justify-content: center;
-        color: var(--text-muted);
-        user-select: none;
-    }
-
-    .meta {
-        display: flex;
-        flex-direction: column;
-        gap: var(--space-1);
-        min-width: 0;
-    }
-
-    .title {
-        font-weight: var(--weight-semibold);
-        font-size: var(--font-base);
-        color: var(--text);
-    }
-
-    .title:hover {
-        color: var(--primary);
-    }
-
-    .target {
-        font-size: var(--font-sm);
-    }
-
-    .muted {
-        color: var(--text-muted);
-    }
-
-    .created {
-        color: var(--text-muted);
-        font-size: var(--font-xs);
-    }
-
     .error {
         color: var(--danger);
     }