style(tests): hoist test_api_tags grounding imports to module level (ruff I001)

CI ruff flagged the in-function import block; move them to the top mirroring
test_ml_suggestions.py's import line, which ruff already accepts.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CDgx8bQS5YrGRK76v8HUnM

tests/test_api_tags.py

@@ -1,4 +1,8 @@
 import pytest
+from sqlalchemy import select
+
+from backend.app.models import ImageRecord, ImageRegion, MLSettings, TagHead, TagKind
+from backend.app.services.tag_service import TagService
 
 pytestmark = pytest.mark.integration
 
@@ -104,13 +108,6 @@ async def test_applied_tag_grounding_returns_winning_region(client, db):
     # Hovering an applied chip fetches the crop that best explains the tag. Here
     # the whole-image vector is orthogonal to the head but a concept crop aligns,
     # so the crop wins the max-over-bag → grounding is that region's box.
-    from sqlalchemy import select
-
-    from backend.app.models import (
-        ImageRecord, ImageRegion, MLSettings, TagHead, TagKind,
-    )
-    from backend.app.services.tag_service import TagService
-
     ver = (await db.execute(
         select(MLSettings).where(MLSettings.id == 1)
     )).scalar_one().embedder_model_version
@@ -148,9 +145,6 @@ async def test_applied_tag_grounding_returns_winning_region(client, db):
 async def test_applied_tag_grounding_no_head(client, db):
     # A tag with no head can't be localized → has_head False, grounding null; the
     # chip shows no overlay. Validates the response contract the frontend reads.
-    from backend.app.models import ImageRecord, TagKind
-    from backend.app.services.tag_service import TagService
-
     img = ImageRecord(
         path="/images/grchip2.jpg", sha256="gd" * 32, size_bytes=1,
         mime="image/jpeg", width=1, height=1, origin="imported_filesystem",