Fix: Make schema creation idempotent

functions/api/admin/create-schema.js

@@ -0,0 +1,13 @@
+export async function onRequestPost({ request, env }) {
+    try {
+        const { admin_pass } = await request.json();
+        if (admin_pass !== env.ADMIN_PASS) return new Response("Unauthorized", { status: 401 });
+
+        const schema = `CREATE TABLE IF NOT EXISTS users (username TEXT PRIMARY KEY, pass_hash TEXT, custom_slugs TEXT);`;
+        await env.D1_EV.exec(schema);
+
+        return new Response("Schema v1 created successfully (if it did not exist).");
+    } catch (e) {
+        return new Response(e.message, { status: 500 });
+    }
+}