derive_master_key now:
- length-prefixes passphrase and image_secret to eliminate concatenation
ambiguity (H1)
- normalizes passphrase to UTF-8 NFC before hashing
- returns Zeroizing<[u8; 32]> so the master key is wiped on drop (H2)
- wraps the intermediate password buffer in Zeroizing for the same reason
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The ManifestEntry was being written with group: None instead of
preserving the entry's existing group value during edits.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Add optional group: Option<String> to both Entry and ManifestEntry for
logical organization (e.g. "work", "personal"). Backwards-compatible via
skip_serializing_if so existing vaults deserialize with group: None.
Includes three new tests verifying round-trip and legacy deserialization.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Document every public function, struct, field, constant, and non-trivial
private function across idfoto-core and idfoto-cli. Module-level docs
explain each module's role in the architecture. Comments explain the "why"
(crypto choices, algorithm design, data model rationale) not just the "what".
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
