feat: Initial commit

@types/fastify/index.d.ts

@@ -0,0 +1,16 @@
+import "fastify";
+
+declare module "fastify" {
+  interface Session {
+    account: { // TODO: Type
+      userId: number;
+      username: string;
+      authenticated: boolean;
+    };
+
+    success?: string;
+    error?: string;
+
+    loginRedirectUri?: string;
+  }
+}