Chore: Upgrade to Angular v18

Chore: Upgrade to Python 3.12
Chore: Upgrade to psycopg3

bookie/src/app/customers/customer-list.resolver.ts

@@ -0,0 +1,10 @@
+import { inject } from '@angular/core';
+import { ResolveFn } from '@angular/router';
+
+import { Customer } from '../core/customer';
+
+import { CustomerService } from './customer.service';
+
+export const customerListResolver: ResolveFn<Customer[]> = () => {
+  return inject(CustomerService).list();
+};