Add basic login

src/lib/auth.svelte.ts

@@ -0,0 +1,38 @@
+import type { NostrUser } from "@nostr/gadgets/metadata";
+import type { WindowNostr } from "@nostr/tools/nip07";
+
+declare global {
+  interface Window {
+    nostr?: WindowNostr;
+  }
+}
+
+let user = $state<NostrUser | null>(null);
+let signer = $state<WindowNostr | null>(null);
+
+export const auth = {
+  get user() {
+    return user;
+  },
+  get signer() {
+    return signer;
+  },
+};
+
+export async function login() {
+  if (!window.nostr) {
+    alert(
+      "No Nostr extension found. Please install a Nostr extension like nos2x.",
+    );
+    return;
+  }
+  const pubkey = await window.nostr.getPublicKey();
+  signer = window.nostr;
+  const { loadNostrUser } = await import("@nostr/gadgets/metadata");
+  user = await loadNostrUser(pubkey);
+}
+
+export function logout() {
+  user = null;
+  signer = null;
+}