Convert vaulty_info, mega_transfers, AdidasUser to LAVA @artifact_processor

[abrignoni]

Converts three more parsers to the LAVA @artifact_processor pattern.

• vaulty_info — flat prefs Key/Value with MD5/PIN brute-force; no timestamps. Refactored the prefs lookup into a single dict pass, replaced the for/else (W0120) brute-force with a clean loop, and added encoding to open().
• mega_transfers — AES-decrypted completed-transfers; transfertimestamp decrypted then → aware UTC datetime (replacing utcfromtimestamp); direction/state lookups hoisted to module constants; switched to open_sqlite_db_readonly.
• AdidasUser — key/value userProperty assembled into one row; createdAt/lastV3SessionSyncAtLocalTime → aware UTC datetime; Image declared in html_columns and NULL-guarded; initialized all fields to '' to remove the E0606 unbound-variable risk.

Verified: byte-compile, decorated 4-arg signature, returns 3-tuple, output_types valid, loader resolves, pylint clean.