feat(series): SeriesManageView + /series/:tagId route + TagCard manage affordance

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

frontend/src/router.js

@@ -5,6 +5,7 @@ import GalleryView from './views/GalleryView.vue'
 import ShowcaseView from './views/ShowcaseView.vue'
 import TagsView from './views/TagsView.vue'
 import ArtistView from './views/ArtistView.vue'
+import SeriesManageView from './views/SeriesManageView.vue'
 
 // The application's front door. `/` redirects here. Changing the front door
 // is a one-line edit (e.g. '/gallery' or '/tags').
@@ -20,6 +21,8 @@ const routes = [
   { path: '/tags',     name: 'tags',     component: TagsView,     meta: { title: 'Tags'     } },
   // Artist detail — no meta.title (reached by clicking an artist, not nav).
   { path: '/artist/:slug', name: 'artist', component: ArtistView },
+  // Series management — no meta.title (reached from a series tag card).
+  { path: '/series/:tagId', name: 'series-manage', component: SeriesManageView },
   { path: '/settings', name: 'settings', component: SettingsView, meta: { title: 'Settings' } },
 
   // FC-3: subscription backbone