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/stores/suggestions.js

@@ -117,9 +117,15 @@ export const useSuggestionsStore = defineStore('suggestions', () => {
   async function aliasAccept(suggestion, canonicalTagId) {
     const imageId = currentImageId
     if (imageId == null) return
+    // The alias MUST be stored under the raw model key — resolution looks up the
+    // raw prediction key, not the normalized display name. Sending display_name
+    // (the old bug) stored an alias that never resolved, so the prediction kept
+    // reappearing unaliased. raw_name is null only for centroid hits, which
+    // can't be aliased (the UI hides the action for them).
+    const aliasString = suggestion.raw_name ?? suggestion.display_name
     await api.post(`/api/images/${imageId}/suggestions/alias`, {
       body: {
-        alias_string: suggestion.display_name,
+        alias_string: aliasString,
         alias_category: suggestion.category,
         canonical_tag_id: canonicalTagId
       }
@@ -133,6 +139,22 @@ export const useSuggestionsStore = defineStore('suggestions', () => {
     })
   }
 
+  // Remove the alias behind an aliased suggestion (the raw prediction reverts to
+  // its unaliased form on reload). The canonical tag stays applied if it was
+  // accepted — this only undoes the model-key→tag mapping.
+  async function removeAlias(suggestion) {
+    const imageId = currentImageId
+    if (imageId == null || suggestion.raw_name == null) return
+    await api.delete(
+      `/api/aliases/${encodeURIComponent(suggestion.raw_name)}/${encodeURIComponent(suggestion.category)}`
+    )
+    if (currentImageId === imageId) {
+      await load(imageId)
+      await loadAll(imageId)
+    }
+    toast({ text: `Alias removed: ${suggestion.display_name}`, type: 'success' })
+  }
+
   async function dismiss(suggestion) {
     const imageId = currentImageId
     if (imageId == null) return
@@ -151,6 +173,6 @@ export const useSuggestionsStore = defineStore('suggestions', () => {
 
   return {
     byCategory, allByCategory, loading, error,
-    load, loadAll, accept, aliasAccept, dismiss
+    load, loadAll, accept, aliasAccept, removeAlias, dismiss
   }
 })