fix: eliminate diagonal dither pattern from display driver

Root cause: Panel_ED2208's epd_quality mode applies _dither_row_rgb_pair
(diagonal bias pattern with dither=140) during _exec_transfer(). Since our
ImagePipeline already does proper Floyd-Steinberg dithering, the driver's
additional dithering was creating visible diagonal artifacts.

Fix: setEpdMode(epd_fastest) selects _dither_row_none (clean nearest-color
lookup, no spatial bias). On Panel_ED2208 this only affects the dither
function — NOT refresh quality or waveform.

Also: default dither_noise setting to OFF since error scatter was targeting
the wrong layer (it made gradient areas fuzzier without fixing the real
problem in the display driver).

Co-authored-by: Cursor <cursoragent@cursor.com>

src/immich_client.h

@@ -21,12 +21,18 @@ struct AssetInfo {
     std::vector<String> people;
 };
 
+struct RandomAsset {
+    String id;
+    String dateTime;
+};
+
 class ImmichClient {
 public:
     void begin(const String& baseUrl, const String& apiKey);
     std::vector<AlbumInfo> fetchAlbums();
     std::vector<String> fetchAlbumAssetIds(const String& albumId);
     std::vector<String> fetchRandomAssetIds(int count = 50);
+    std::vector<RandomAsset> fetchRandomAssets(int count = 50);
     std::vector<String> fetchFavoriteAssetIds();
     AssetInfo fetchAssetInfo(const String& assetId);
     bool downloadAsset(const String& assetId, ImageQuality quality,