Rewrite in TS

frontend/src/lib/constants.ts

@@ -1,3 +1,5 @@
+import type { Filters } from '../types';
+
 // Filter configuration constants
 // Should match backend pipeline/config.py
 
@@ -9,7 +11,7 @@ export const PRICE_MIN = 0;
 export const PRICE_MAX = 5000000; // £5M max for slider, but no server-side cap
 export const PRICE_STEP = 50000;
 
-export const DEFAULT_FILTERS = {
+export const DEFAULT_FILTERS: Filters = {
   minYear: 2020,
   maxYear: YEAR_MAX,
   minPrice: PRICE_MIN,

frontend/src/lib/utils.js

@@ -1,4 +0,0 @@
-import { clsx } from 'clsx';
-import { twMerge } from 'tailwind-merge';
-
-export const cn = (...inputs) => twMerge(clsx(inputs));

frontend/src/lib/utils.ts

@@ -0,0 +1,4 @@
+import { clsx, type ClassValue } from 'clsx';
+import { twMerge } from 'tailwind-merge';
+
+export const cn = (...inputs: ClassValue[]): string => twMerge(clsx(inputs));