Add APISigner and AdminSigner classes, implement NostrSigner interface

scripts/admin.ts

@@ -1,5 +1,5 @@
 import * as pipeline from '@/pipeline.ts';
-import { signAdminEvent } from '@/sign.ts';
+import { AdminSigner } from '@/signers/AdminSigner.ts';
 import { type EventStub } from '@/utils/api.ts';
 import { nostrNow } from '@/utils.ts';
 
@@ -12,7 +12,9 @@ switch (Deno.args[0]) {
 }
 
 async function publish(t: EventStub) {
-  const event = await signAdminEvent({
+  const signer = new AdminSigner();
+
+  const event = await signer.signEvent({
     content: '',
     created_at: nostrNow(),
     tags: [],