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>

apps/api-server/src/constants.ts

@@ -22,7 +22,7 @@ export const getAllowedOrigins = (): string[] => {
 
   // Default to localhost origins for development
   return [
-    `http://localhost:${String(DEFAULT_PORT)}`,
+    `http://localhost:${DEFAULT_PORT.toString()}`,
     "http://localhost:6827",
     "http://localhost:6828",
   ];