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>

tests/test_api_aliases.py

@@ -37,3 +37,24 @@ async def test_create_list_delete(client, db):
 async def test_create_requires_fields(client):
     resp = await client.post("/api/aliases", json={"alias_string": "x"})
     assert resp.status_code == 400
+
+
+@pytest.mark.asyncio
+async def test_list_for_tag_endpoint(client, db):
+    tag = await TagService(db).find_or_create("TagSide", TagKind.character)
+    await db.commit()
+    await client.post(
+        "/api/aliases",
+        json={
+            "alias_string": "ts_key",
+            "alias_category": "character",
+            "canonical_tag_id": tag.id,
+        },
+    )
+
+    resp = await client.get(f"/api/tags/{tag.id}/aliases")
+    assert resp.status_code == 200
+    body = await resp.get_json()
+    assert body == [{"alias_string": "ts_key", "alias_category": "character"}]
+
+    assert (await client.get("/api/tags/99999999/aliases")).status_code == 404