fix(gallery): ruff C408 (dict literal) + panel auto-open on deep-link

Rewrite facets() common/plat_scope as dict literals (C408). Open the refine
panel via a watch on hasRefineFilters rather than reading filter state at
bar-setup time — the parent applies the URL query in its onMounted, after the
bar child has set up, so the initial read was always the default (empty) state.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/app/services/gallery_service.py

@@ -431,10 +431,10 @@ class GalleryService:
         column predicate on ImageRecord.
         """
         _require_single_filter(tag_ids, post_id, artist_id)
-        common = dict(
-            tag_ids=tag_ids, post_id=post_id,
-            artist_id=artist_id, media_type=media_type,
-        )
+        common = {
+            "tag_ids": tag_ids, "post_id": post_id,
+            "artist_id": artist_id, "media_type": media_type,
+        }
 
         # total — the full active filter (the headline result count).
         total = (await self.session.execute(
@@ -448,10 +448,10 @@ class GalleryService:
         # platforms — scope minus the platform selection. Inner-join
         # provenance→source and COUNT(DISTINCT image) per platform (a
         # cross-posted image counts under each of its platforms).
-        plat_scope = dict(
-            common, untagged=untagged, no_artist=no_artist,
-            date_from=date_from, date_to=date_to,
-        )
+        plat_scope = {
+            **common, "untagged": untagged, "no_artist": no_artist,
+            "date_from": date_from, "date_to": date_to,
+        }
         src = aliased(Source)
         plat_stmt = (
             select(src.platform, func.count(distinct(ImageRecord.id)))