fix(server): use hash instead of file counting for the cache key

server/api/gallery.get.ts

@@ -1,5 +1,6 @@
 import { readdir } from "fs/promises";
 import { join } from "path";
+import { createHash } from "crypto";
 import exifr from "exifr";
 import { z } from "zod";
 
@@ -77,7 +78,9 @@ export default defineCachedEventHandler(
         const imageFiles = files.filter((file) =>
           /\.(jpg|jpeg|png|webp)$/i.test(file),
         );
-        return `gallery:${imageFiles.length}`;
+        const filesConcat = imageFiles.sort().join("");
+        const hash = createHash("sha256").update(filesConcat).digest("hex");
+        return `gallery:${hash}`;
       } catch {
         return "gallery:0";
       }