feat(detail): link genre and tag chips to the filtered catalogue

Genre chips now deep-link to /?genres=<id> and user-tag chips to
/?tags=<id>, reusing the homepage catalogue's existing filter params —
turning the detail page's metadata into one-tap discovery. Tag chips keep
their remove affordance (the Chip's href branch preventDefaults the remove
button). e2e asserts both chip hrefs.

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

frontend/src/routes/manga/[id]/+page.svelte

@@ -426,7 +426,7 @@
                 <div class="chip-row" data-testid="manga-genres">
                     <span class="chip-row-label">Genres</span>
                     {#each genres as g (g.id)}
-                        <Chip label={g.name} />
+                        <Chip label={g.name} href={`/?genres=${g.id}`} testid={`genre-chip-${g.id}`} />
                     {/each}
                 </div>
             {/if}
@@ -436,6 +436,8 @@
                 {#each tags as t (t.id)}
                     <Chip
                         label={t.name}
+                        href={`/?tags=${t.id}`}
+                        testid={`tag-chip-${t.id}`}
                         variant="soft"
                         onRemove={session.user && t.added_by === session.user.id
                             ? () => removeTag(t)