fix(aliases): store modal alias under raw model key + make aliases visible/manageable

The headline bug: aliases created from the modal NEVER resolved. Create
sent the normalized display name ('Sword', 'Uchiha Sasuke') while
resolution keys on the raw booru model key ('sword', 'uchiha_sasuke',
case-sensitive) — so the mapping was stored under a key nothing looks up,
and the prediction kept reappearing unaliased. The raw key wasn't even in
the /suggestions response, so the modal couldn't send it.

- Suggestion now carries raw_name (the model key an alias must use) and
  via_alias (surfaced via an operator alias); both serialized by the API.
- Modal alias-create sends raw_name, not display_name (the fix). Aliased
  suggestions show an 'alias' badge and a 'Remove alias' action; 'Treat as
  alias for…' is hidden for centroid hits (no model key) and already-aliased
  rows.
- Tag-side management: TagCard ⋮ → 'Aliases…' opens a dialog listing the
  model keys that fold into a tag, with remove (GET /api/tags/<id>/aliases +
  AliasService.list_for_tag). Creation stays in the modal suggestion flow.

Tests: full API round-trip locking the raw-key contract (raw_name exposed →
alias authored with it → resolves + via_alias on a later image);
list_for_tag (service + API); via_alias/raw_name on the existing service
suggestion tests. No migration.

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

frontend/src/components/discovery/TagAliasesDialog.vue

@@ -0,0 +1,99 @@
+<template>
+  <v-card>
+    <v-card-title class="fc-aliasdlg__title">
+      Aliases for <strong>{{ tag?.name }}</strong>
+    </v-card-title>
+    <v-card-text>
+      <p class="text-caption mb-3">
+        Model keys the tagger predicts that resolve to this tag — so a prediction
+        like <code>{{ exampleKey }}</code> shows as “{{ tag?.name }}” instead of a
+        separate tag. Create new aliases from a suggestion’s ⋮ menu in the image
+        view; here you can see and remove them.
+      </p>
+
+      <div v-if="loading" class="fc-aliasdlg__loading">
+        <v-progress-circular indeterminate color="accent" size="24" />
+      </div>
+      <v-alert v-else-if="error" type="error" variant="tonal" density="compact">
+        {{ error }}
+      </v-alert>
+      <div v-else-if="rows.length === 0" class="text-caption fc-aliasdlg__empty">
+        No aliases yet. In the image view, open a tagger suggestion’s ⋮ menu and
+        choose “Treat as alias for…” to map it to this tag.
+      </div>
+      <v-list v-else density="compact" class="fc-aliasdlg__list">
+        <v-list-item
+          v-for="r in rows" :key="`${r.alias_string}/${r.alias_category}`"
+        >
+          <template #prepend>
+            <code class="fc-aliasdlg__key">{{ r.alias_string }}</code>
+          </template>
+          <v-list-item-subtitle>{{ r.alias_category }}</v-list-item-subtitle>
+          <template #append>
+            <v-btn
+              icon="mdi-delete" size="x-small" variant="text" color="error"
+              :aria-label="`Remove alias ${r.alias_string}`"
+              @click="remove(r)"
+            />
+          </template>
+        </v-list-item>
+      </v-list>
+    </v-card-text>
+    <v-card-actions>
+      <v-spacer />
+      <v-btn @click="$emit('close')">Close</v-btn>
+    </v-card-actions>
+  </v-card>
+</template>
+
+<script setup>
+import { computed, onMounted, ref } from 'vue'
+import { useApi } from '../../composables/useApi.js'
+
+const props = defineProps({ tag: { type: Object, required: true } })
+defineEmits(['close'])
+
+const api = useApi()
+const rows = ref([])
+const loading = ref(false)
+const error = ref(null)
+
+// Illustrative booru-style key for the helper copy (lowercase, underscores).
+const exampleKey = computed(() =>
+  (props.tag?.name || 'tag').toLowerCase().replace(/\s+/g, '_')
+)
+
+async function reload() {
+  loading.value = true
+  error.value = null
+  try {
+    rows.value = await api.get(`/api/tags/${props.tag.id}/aliases`)
+  } catch (e) {
+    error.value = e.message || String(e)
+  } finally {
+    loading.value = false
+  }
+}
+
+async function remove(r) {
+  await api.delete(
+    `/api/aliases/${encodeURIComponent(r.alias_string)}/${encodeURIComponent(r.alias_category)}`
+  )
+  rows.value = rows.value.filter(
+    x => !(x.alias_string === r.alias_string && x.alias_category === r.alias_category)
+  )
+}
+
+onMounted(reload)
+</script>
+
+<style scoped>
+.fc-aliasdlg__loading,
+.fc-aliasdlg__empty { padding: 12px 0; }
+.fc-aliasdlg__key,
+code {
+  background: rgb(var(--v-theme-surface-light));
+  padding: 1px 6px; border-radius: 4px;
+  font-family: 'JetBrains Mono', monospace; font-size: 12px;
+}
+</style>

frontend/src/components/discovery/TagCard.vue

@@ -53,6 +53,11 @@
               prepend-icon="mdi-book-open-page-variant"
               @click="$emit('set-fandom', card)"
             />
+            <v-list-item
+              title="Aliases…"
+              prepend-icon="mdi-tag-multiple"
+              @click="$emit('aliases', card)"
+            />
             <v-list-item
               title="Merge with…"
               prepend-icon="mdi-call-merge"
@@ -78,6 +83,7 @@ import KebabMenu from '../common/KebabMenu.vue'
 const props = defineProps({ card: { type: Object, required: true } })
 const emit = defineEmits([
   'open', 'rename', 'manage', 'read', 'merge-with', 'delete', 'set-fandom',
+  'aliases',
 ])
 
 const editing = ref(false)