feat(fc2b): add tag rename (PATCH /api/tags/<id>) + /api/ml admin

Rename returns 409 on collision (frontend shows FC-2c merge hint), 400
on empty. ml_admin: GET/PATCH settings (thresholds + min_reference;
model versions read-only here), POST backfill / recompute-centroids
returning 202 + celery task id. Tests integration-marked, eager Celery.

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

backend/app/api/__init__.py

@@ -18,6 +18,7 @@ def all_blueprints() -> list[Blueprint]:
     from .allowlist import allowlist_bp
     from .gallery import gallery_bp
     from .import_admin import import_admin_bp
+    from .ml_admin import ml_admin_bp
     from .settings import settings_bp
     from .suggestions import suggestions_bp
     from .tags import tags_bp
@@ -30,4 +31,5 @@ def all_blueprints() -> list[Blueprint]:
         suggestions_bp,
         allowlist_bp,
         aliases_bp,
+        ml_admin_bp,
     ]

backend/app/api/ml_admin.py

@@ -0,0 +1,87 @@
+"""ML admin API: settings, backfill trigger, centroid recompute trigger."""
+
+from quart import Blueprint, jsonify, request
+
+from ..extensions import make_engine, make_session_factory
+from ..models import MLSettings
+
+ml_admin_bp = Blueprint("ml_admin", __name__, url_prefix="/api/ml")
+
+_engine = None
+_Session = None
+
+
+def _session_factory():
+    global _engine, _Session
+    if _engine is None:
+        _engine = make_engine()
+        _Session = make_session_factory(_engine)
+    return _Session
+
+
+_EDITABLE = (
+    "suggestion_threshold_artist",
+    "suggestion_threshold_character",
+    "suggestion_threshold_copyright",
+    "suggestion_threshold_general",
+    "centroid_similarity_threshold",
+    "min_reference_images",
+)
+
+
+@ml_admin_bp.route("/settings", methods=["GET"])
+async def get_settings():
+    from sqlalchemy import select
+
+    Session = _session_factory()
+    async with Session() as session:
+        s = (
+            await session.execute(select(MLSettings).where(MLSettings.id == 1))
+        ).scalar_one()
+    return jsonify(
+        {
+            "suggestion_threshold_artist": s.suggestion_threshold_artist,
+            "suggestion_threshold_character": s.suggestion_threshold_character,
+            "suggestion_threshold_copyright": s.suggestion_threshold_copyright,
+            "suggestion_threshold_general": s.suggestion_threshold_general,
+            "centroid_similarity_threshold": s.centroid_similarity_threshold,
+            "min_reference_images": s.min_reference_images,
+            "tagger_model_version": s.tagger_model_version,
+            "embedder_model_version": s.embedder_model_version,
+        }
+    )
+
+
+@ml_admin_bp.route("/settings", methods=["PATCH"])
+async def patch_settings():
+    from sqlalchemy import select
+
+    body = await request.get_json()
+    if not isinstance(body, dict):
+        return jsonify({"error": "body must be an object"}), 400
+    Session = _session_factory()
+    async with Session() as session:
+        s = (
+            await session.execute(select(MLSettings).where(MLSettings.id == 1))
+        ).scalar_one()
+        for field in _EDITABLE:
+            if field in body:
+                setattr(s, field, body[field])
+        await session.commit()
+    return await get_settings()
+
+
+@ml_admin_bp.route("/backfill", methods=["POST"])
+async def trigger_backfill():
+    from ..tasks.ml import backfill
+
+    r = backfill.delay()
+    return jsonify({"celery_task_id": r.id}), 202
+
+
+@ml_admin_bp.route("/recompute-centroids", methods=["POST"])
+async def trigger_recompute():
+    from ..tasks.ml import recompute_centroids
+
+    r = recompute_centroids.delay()
+    return jsonify({"celery_task_id": r.id}), 202

backend/app/api/tags.py

@@ -124,3 +124,24 @@ async def remove_tag_from_image(image_id: int, tag_id: int):
         await svc.remove_from_image(image_id, tag_id)
         await session.commit()
     return "", 204
+
+
+@tags_bp.route("/tags/<int:tag_id>", methods=["PATCH"])
+async def rename_tag(tag_id: int):
+    body = await request.get_json()
+    if not body or "name" not in body:
+        return jsonify({"error": "name required"}), 400
+    Session = _session_factory()
+    async with Session() as session:
+        svc = TagService(session)
+        try:
+            tag = await svc.rename(tag_id, body["name"])
+        except TagValidationError as exc:
+            # Collision → 409 so the frontend can show the FC-2c merge hint.
+            msg = str(exc)
+            status = 409 if "already exists" in msg else 400
+            return jsonify({"error": msg}), status
+        await session.commit()
+        return jsonify(
+            {"id": tag.id, "name": tag.name, "kind": tag.kind.value}
+        )

tests/test_api_ml_admin.py

@@ -0,0 +1,67 @@
+import pytest
+
+from backend.app import create_app
+from backend.app.celery_app import celery
+from backend.app.models import TagKind
+from backend.app.services.tag_service import TagService
+
+pytestmark = pytest.mark.integration
+
+
+@pytest.fixture(autouse=True)
+def eager():
+    celery.conf.task_always_eager = True
+    yield
+    celery.conf.task_always_eager = False
+
+
+@pytest.fixture
+async def app():
+    return create_app()
+
+
+@pytest.fixture
+async def client(app):
+    async with app.test_client() as c:
+        yield c
+
+
+@pytest.mark.asyncio
+async def test_get_and_patch_settings(client):
+    resp = await client.get("/api/ml/settings")
+    assert resp.status_code == 200
+    body = await resp.get_json()
+    assert body["suggestion_threshold_general"] == pytest.approx(0.95)
+
+    resp = await client.patch(
+        "/api/ml/settings", json={"suggestion_threshold_general": 0.90}
+    )
+    assert resp.status_code == 200
+    assert (await resp.get_json())["suggestion_threshold_general"] == pytest.approx(0.90)
+
+
+@pytest.mark.asyncio
+async def test_backfill_and_recompute_trigger(client):
+    r1 = await client.post("/api/ml/backfill")
+    assert r1.status_code == 202
+    r2 = await client.post("/api/ml/recompute-centroids")
+    assert r2.status_code == 202
+
+
+@pytest.mark.asyncio
+async def test_rename_tag(client, db):
+    tag = await TagService(db).find_or_create("oldname", TagKind.character)
+    await db.commit()
+    resp = await client.patch(f"/api/tags/{tag.id}", json={"name": "New Name"})
+    assert resp.status_code == 200
+    assert (await resp.get_json())["name"] == "New Name"
+
+
+@pytest.mark.asyncio
+async def test_rename_collision_409(client, db):
+    svc = TagService(db)
+    await svc.find_or_create("Taken", TagKind.character)
+    other = await svc.find_or_create("Mover", TagKind.character)
+    await db.commit()
+    resp = await client.patch(f"/api/tags/{other.id}", json={"name": "Taken"})
+    assert resp.status_code == 409