fix: ruff C416 (dict() over comprehension) + frontend test playlistIds rename

- heads.py: conf_map = dict(conf) instead of a dict comprehension (ruff C416).
- postCard.spec.js: the modal-playlist rename (postImageIds→playlistIds) missed
  this frontend test (grep was src-only); update the expected call args.

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

frontend/test/components/postCard.spec.js

@@ -80,6 +80,6 @@ describe('PostCard', () => {
     const w = mountComponent(PostCard, { props: { post }, pinia })
     await w.find('.fc-post-card__hero').trigger('click')
     await flushPromises()
-    expect(openSpy).toHaveBeenCalledWith(10, { postImageIds: [10, 11] })
+    expect(openSpy).toHaveBeenCalledWith(10, { playlistIds: [10, 11] })
   })
 })