Harden CMS security and theme contrast

src/lib/auth/session-user.ts

@@ -0,0 +1,9 @@
+export function sessionUserId(value: unknown): number | null {
+  const id = typeof value === "string" && /^\d+$/.test(value) ? Number(value) : NaN;
+  return Number.isSafeInteger(id) && id > 0 ? id : null;
+}
+
+export function databaseUserId(value: bigint): number | null {
+  const id = Number(value);
+  return Number.isSafeInteger(id) && id > 0 ? id : null;
+}