Restores Unicode-aware case-insensitive substring search (approach A of #227).
Paging (#223) moved search to a SQL LIKE scan whose case-folding is ASCII-only,
so non-ASCII terms stopped matching case-insensitively.
Adds per-field casefold columns to `messages` (senderFold/senderEmailFold/
subjectFold/snippetFold), each = Kotlin lowercase() of its source (Unicode-aware).
Per-field (not one concatenated column) because the fields are maintained by
partial UPDATEs that don't carry all four: toEntity sets all folds, updateBody
keeps snippetFold in sync, updateHeaderContent keeps the header folds -- via thin
DAO default-method wrappers so the five call sites are unchanged. Search matches
the fold columns with a pattern built from the lowercased query.
Schema v18->v19 (additive; ASCII lower() backfill, non-ASCII rows re-fold on next
write). Adds a MigrationTest v18->v19 case and a repo test asserting the query is
casefolded.
Closes#232
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Jason Ross
JMR-devandClaude Opus 4.8