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

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

frontend/src/components/discovery/TagCard.vue

@@ -19,6 +19,12 @@
             class="fc-tagcard__edit" size="14" icon="mdi-pencil"
             @click.stop="startEdit"
           />
+          <v-icon
+            v-if="card.kind === 'series'"
+            class="fc-tagcard__edit" size="14"
+            icon="mdi-book-open-page-variant"
+            title="Manage series" @click.stop="$emit('manage', card.id)"
+          />
         </template>
         <v-text-field
           v-else
@@ -43,7 +49,7 @@
 import { ref } from 'vue'
 
 const props = defineProps({ card: { type: Object, required: true } })
-const emit = defineEmits(['open', 'rename'])
+const emit = defineEmits(['open', 'rename', 'manage'])
 
 const editing = ref(false)
 const draft = ref('')
@@ -76,8 +82,8 @@ function submit() {
 .fc-tagcard__previews img { width: 100%; height: 100%; object-fit: cover; }
 .fc-tagcard__noimg {
   grid-column: 1 / -1; display: flex; align-items: center;
-  justify-content: center; color: rgb(var(--v-theme-on-surface));
-  opacity: 0.5; font-size: 12px;
+  justify-content: center;
+  color: rgb(var(--v-theme-on-surface-variant)); font-size: 12px;
 }
 .fc-tagcard__body { padding: 8px 12px; }
 .fc-tagcard__name { font-weight: 600; }