refactor: proper record type + MASL spec conformance
- new collection: systems.witchcraft.archive.bundle (was ing.dasl.masl)
- MASL data in .masl field with CID strings in src (spec-conformant)
- ATProto blob refs in separate .blobs map for content retrieval
- archive metadata (url, title, capturedAt) at record top level
- backwards-compatible: list/search/verify handle legacy records
- thanks to nel.pet for the spec feedback!