feat(editor): post type on top (segmented) + type-aware inputs
Bart's UX feedback: the post-type selector moved from the bottom Meta
section to a prominent segmented control at the top of the editor, above
the body. The selected type now reveals its own input:
- Audio -> inline upload (drag/drop), transcodes server-side and drops
the track straight into the post (no more /admin/audio detour)
- Video -> paste a URL -> embed chip
- Foto -> hint toward cover + insert-image
Reuses the existing /admin/audio/upload endpoint (returns {ok,id}) and the
editor's insertChip(). Adds pedit.* i18n keys (nl/en/de).
Co-Authored-By: Claude <noreply@…>