refactor: mark dead exports with TODO, deduplicate field sanitization, fix import placement

src/lib/foundation/errors.ts

@@ -49,6 +49,7 @@ export class RateLimitError extends DomainError {
 	}
 }
 
+// TODO: Check of dit weg kan — niet geïmporteerd in de codebase
 export class ConflictError extends DomainError {
 	constructor(message: string) {
 		super(message, 409);