Add comprehensive test suite (174 tests) covering encoding, schema,
image, database CRUD, and PNG round-trip. Fix critical bugs:
- PNG compression: replace non-functional zlibCompress with pako.deflate
- PNG import: add CRC validation, support all filter types (Sub/Up/Avg/Paeth)
- Input validation: validate records against schema before insert
- Index overflow: dynamic dataStartRing prevents index/data ring overlap
- Image expansion: expand before writes instead of after to prevent OOB
- update() read bug: search index from end to find latest entry, not deleted one
- String encoding: enforce 511-byte max length
- Index ring count: use 6 bits (2 pixels) instead of 3 bits for >7 ring support
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
