Convert googleMessages, kijijiConversations, smyfilesOpHistory to LAVA @artifact_processor

[abrignoni]

Converts three more parsers to the LAVA @artifact_processor pattern.

• googleMessages — flat message table; parts.timestamp raw → aware UTC datetime (replacing SQL datetime(...,'unixepoch')); Message Sender marked phonenumber.
• kijijiConversations — per-thread JSON message expansion retained via the AppendMessageRowsToDataList helper; Date Sent kept as the app's raw value (format unverified); kept the conversations table-exists guard.
• smyfilesOpHistory — Samsung My Files op-history with the custom char-substitution decoder; Android-version gate retained; Operation Date (Handset Timezone) kept as the stored handset-local string. Fixed paths (was a bare string, not a 1-tuple → glob iterated char-by-char) and now closes the DB handle in the helper.

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