Bumps package.json/server.json/SIGN_CLI_VERSION to 0.7.0 (minor: the audit
security fixes change PDF-verify and MCP behavior in user-visible, breaking
ways) and dates the CHANGELOG [0.7.0] section. Also corrects SIGN_CLI_VERSION,
which had drifted to 0.6.4 while the published package was 0.6.5.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>