Relicense from AGPL-3.0-only to MIT
Switch all license declarations to MIT per founder-approved decision.
Updated: LICENSE, package.json, package-lock.json, CLAUDE.md, README.md,
CONTRIBUTING.md, and SPDX headers in all 73 source files.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>