Pickaxe Embed SSO WordPress Plugin v0.1.0

First pilot build of the Pickaxe Embed SSO WordPress plugin.\n\nIncludes:\n- Logged-in WordPress user detection via native auth\n- REST endpoint at /wp-json/pickaxe-sso/v1/embed-token\n- ES256 signed JWT handoff using the same embed SSO contract as the local NextAuth mock\n- [pickaxe_embed] shortcode\n- Settings page for customer ID, issuer, audience, key ID, private key, embed origin, and script URL\n\nInstall by downloading pickaxe-embed-sso.zip and uploading it in WordPress Admin > Plugins > Add New > Upload Plugin.\n\nPilot caveat: this has not yet been linted in a PHP runtime on this machine; validate activation on a staging WordPress install before production use.