feat: Updated screensaver image mode fetches random images (#2430)

BREAKING CHANGE: The `screensaver` image mode now shows a random image
from [picsum.photos](picsum.photos) instead of the embedded default
image. If you previously set `image.mode: screensaver`, change it to
`image.mode: default` to restore the previous behavior.

src/config/schema/common/image.ts

@@ -2,16 +2,25 @@ import { z } from 'zod';
 
 export const imageBaseConfigDefault = {
   mode: 'auto' as const,
-  refresh_seconds: 1,
+  refresh_seconds: 'auto' as const,
 };
 
-const IMAGE_MODES = ['auto', 'camera', 'entity', 'screensaver', 'url'] as const;
+const IMAGE_MODES = [
+  'auto',
+  'camera',
+  'default',
+  'entity',
+  'screensaver',
+  'url',
+] as const;
 export type ImageMode = (typeof IMAGE_MODES)[number];
 
 export const imageBaseConfigSchema = z.object({
   mode: z.enum(IMAGE_MODES).default(imageBaseConfigDefault.mode),
 
-  refresh_seconds: z.number().min(0).default(imageBaseConfigDefault.refresh_seconds),
+  refresh_seconds: z
+    .union([z.literal('auto'), z.number().min(0)])
+    .default(imageBaseConfigDefault.refresh_seconds),
 
   url: z.string().optional(),
   entity: z.string().optional(),