feat: migrate to UnifiedPush

lib/push/base64url.ts

@@ -0,0 +1,14 @@
+export function b64uEncode(buf: Buffer | Uint8Array): string {
+  const b = Buffer.isBuffer(buf) ? buf : Buffer.from(buf);
+  return b
+    .toString('base64')
+    .replace(/\+/g, '-')
+    .replace(/\//g, '_')
+    .replace(/=+$/, '');
+}
+
+export function b64uDecode(value: string): Buffer {
+  const padded = value.replace(/-/g, '+').replace(/_/g, '/');
+  const padLen = (4 - (padded.length % 4)) % 4;
+  return Buffer.from(padded + '='.repeat(padLen), 'base64');
+}