Save in-progress keysat integration and StartOS 0.4 work

Snapshot of the working tree before cleanup. Captures:
- Keysat licensing: server/license.js, /api/license/* endpoints in
  server/index.js, activation modal in public/index.html, embedded
  Ed25519 issuer key (assets/issuer.pub).
- StartOS 0.4 expansion: setApiKey action, version files v0.1.1
  through v0.1.15, file-models/config.json.ts, manifest updates.
- Self-hosted registry server (startos-registry/).
- Build/deploy scripts (bin/bump-version.sh, bin/deploy.sh, vendored
  yt-dlp binary), .gitignore, .deploy.env.example.
- Recent design docs (KEYSAT_INTEGRATION.md, UPGRADE-DESIGN.md) —
  retained here so they remain recoverable when removed in the
  follow-up cleanup commit.

startos-registry/node_modules/math-intrinsics/mod.js

@@ -0,0 +1,9 @@
+'use strict';
+
+var $floor = require('./floor');
+
+/** @type {import('./mod')} */
+module.exports = function mod(number, modulo) {
+	var remain = number % modulo;
+	return $floor(remain >= 0 ? remain : remain + modulo);
+};