ctime is ambiguous cross-platform (macOS birth time vs Linux inode change
time), never used operationally (scanning triggers on mtime), cannot be
restored on either platform, and was write-only forensic data with no
consumer.
Removes ctime from:
- files table schema (schema.sql)
- File struct (models.go)
- all SQL queries and scan targets (files.go)
- scanner file metadata collection (scanner.go)
- all test files
- ARCHITECTURE.md and docs/DATAMODEL.md
closes#54
Document the data model, type instantiation flow, and module
responsibilities. Covers chunker, packer, vaultik, cli, snapshot,
and database modules with detailed explanations of relationships
between File, Chunk, Blob, and Snapshot entities.
