feat: add darktable web API interface with gallery, image detail, and settings screens

- Implemented main entry point for React application in `main.jsx`.
- Created `Gallery` component for displaying images with infinite scroll and pull-to-refresh functionality.
- Developed `ImageDetail` component for showing detailed information and actions for selected images.
- Added `Settings` component for configuring API connection settings.
- Integrated Vite for build and development with PWA support.
- Implemented caching strategies for API responses and image previews using Workbox.

contrib/darktable-api/preview.lua

@@ -79,13 +79,21 @@ end
 function M.get(image_id, image_path, filename, size_param)
   local mip = size_to_mip(size_param)
 
-  -- 1. Walk mip levels downward until we find a cached JPEG.
+  -- 1. Walk mip levels: first downward (smaller = smaller file, faster),
+  --    then upward (larger mip levels, let the browser scale down).
+  --    This ensures we serve something even when only higher-resolution
+  --    mipmaps have been cached (e.g. darktable only wrote levels 2-4).
   local base = mipmap_base()
   for level = mip, 0, -1 do
     local path = string.format("%s.d/%d/%d.jpg", base, level, image_id)
     local data = read_file(path)
     if data then return data, "image/jpeg" end
   end
+  for level = mip + 1, 5 do
+    local path = string.format("%s.d/%d/%d.jpg", base, level, image_id)
+    local data = read_file(path)
+    if data then return data, "image/jpeg" end
+  end
 
   -- 2. Try exiftool to extract the embedded EXIF thumbnail from the source file.
   if image_path and filename then