fix: escape dots in FTS5 search queries
FTS5 interprets dots as column filter operators, so a query like
"alice.test" was parsed as "search column 'alice' for 'test'" instead
of matching the handle. Adding dot to the escape regex converts it to
"alice test" which matches correctly.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>