FTS5 prefix matching misses mid-word substrings (e.g. "ebook" in
"notebook"). When FTS5 returns zero results, fall back to LIKE
query on title and category with proper wildcard escaping. 4 new
tests, 757 total.
Also marks completed plan files (search, admin-redesign,
setup-wizard, products-context) with correct status.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>