fix: make order search case-insensitive

instr() in SQLite compares bytes, so searching for a customer name
in uppercase (e.g. "JOHN") silently missed lowercase-stored matches
like "John". Lowercase both sides of the order number, name, and
email comparisons so search matches regardless of the case staff
paste in.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/api/src/orders/order-search-assignment-1.test.ts

@@ -7,7 +7,7 @@ let app: AppWithContext;
 let employeeCookie = "";
 
 function firstHeader(value: string | string[] | undefined) {
-  return Array.isArray(value) ? (value[0] ?? "") : value ?? "";
+  return Array.isArray(value) ? value[0] : value ?? "";
 }
 
 async function login(username: string) {