Replace String() calls with .toString()/.toLocaleString() per ast-grep rule

- Add formatError() helper in CLI to safely handle unknown error types
- Add uniqueTestId() helper for generating unique test identifiers
- Replace String(id) with id.toString() for database ID conversions
- Replace String(n) with n.toLocaleString() for user-facing number formatting
- Fix TypeScript errors in test files (undefined checks, unused variables)
- Update lint commands to include ast-grep scanning

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/utils/src/hash-password.ts

@@ -63,7 +63,7 @@ export const hashPassword = async (password: string): Promise<string> => {
   const saltB64 = toBase64(salt.buffer);
   const hashB64 = toBase64(derivedBits);
 
-  return `$${ALGORITHM}$${String(ITERATIONS)}$${saltB64}$${hashB64}`;
+  return `$${ALGORITHM}$${ITERATIONS.toString()}$${saltB64}$${hashB64}`;
 };
 
 export const verifyPassword = async (