Fix fan_mode type to match backend API ('auto' | 'curve')

frontend/src/types.ts

@@ -73,7 +73,7 @@ export interface FanPoint {
 
 export interface FanState {
   fan_pct: number | null;
-  fan_mode: number | null;
+  fan_mode: 'auto' | 'curve' | null;
   min_fan_pct: number | null;
   max_fan_pct: number | null;
   curve: FanPoint[] | null;