feat: implement background color and night mode settings in the TV control app

tv/src/types.ts

@@ -3,9 +3,25 @@ export interface TextState {
   title: string;
 }
 
+export interface NightModeSettings {
+  /** Whether night mode scheduling is active */
+  enabled: boolean;
+  /** Start of night window, "HH:MM" 24-hour */
+  start_time: string;
+  /** End of night window (exclusive), "HH:MM" 24-hour */
+  end_time: string;
+  /** Text shown on image rotator cards during night mode */
+  message: string;
+  /** When true, hide background image/colour and use near-black */
+  dim_background: boolean;
+}
+
 export interface SettingsState {
-  /** Portrait background image URL (height > width). Empty string = no background. */
+  /** Landscape background image URL. Empty string = no background. */
   background_url: string;
+  /** CSS colour string for the TV background. Default "#000000". */
+  background_color: string;
+  night_mode: NightModeSettings;
 }
 
 export interface ImagePopupState {