D1 caps LIKE/GLOB pattern length at 50 bytes. /admin/address and
/admin/users wrapped the query as `%${query}%` and fed it to LIKE,
so searching by a full email address crashed with "LIKE or GLOB
pattern too complex". Fall back to instr() above the 50-byte
threshold.
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>