docs(m7): spec for #352 playlists CRUD (slice 1 of 3)
Manual playlists only — schema (migration 0014), backend service +
collage generator, /api/playlists* endpoints, /playlists list +
detail pages, AddToPlaylistMenu wired into TrackMenu's reserved slot.
10 locked decisions captured: private-by-default, manual-only,
api-only (no Subsonic), 2×2 collage always (glyph fills missing
cells), soft-mark cascade with denormalized snapshot, full-list
reorder, inline collage gen, composite PK on (playlist_id, position),
denormalized track_count + duration_sec rollups.
Slices 2 (system-generated daily mixes) and 3 (home-page playlists
row) are sibling cycles; per v1=full-product all three ship before
tag.
bvandeusen
65bb4e6dfd