fix(lint): use dict() not a dict-comprehension in tag_stats (C416)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ttrj5P7upUTueSfoJcxEqa

backend/app/api/tags.py

@@ -127,15 +127,15 @@ async def tag_stats(tag_id: int):
         tag = await session.get(Tag, tag_id)
         if tag is None:
             return jsonify({"error": "not found"}), 404
-        by_source = {
+        by_source = dict(
-            src: n for src, n in (
+            (
                 await session.execute(
                     select(image_tag.c.source, func.count())
                     .where(image_tag.c.tag_id == tag_id)
                     .group_by(image_tag.c.source)
                 )
             ).all()
-        }
+        )
         rejected = (
             await session.execute(
                 select(func.count())