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/api.lua

@@ -210,7 +210,15 @@ function M.get_preview(req)
     end
   end
 
-  return err(404, "no_preview", "no cached preview available for image " .. id)
+  -- No cached preview exists.  Enqueue a full-pipeline thumbnail generation
+  -- so the bridge renders one; the client should retry after a few seconds.
+  enqueue_refresh(id)
+  return 202, json.encode({
+    status      = "generating",
+    image_id    = id,
+    retry_after = 4,
+    message     = "thumbnail is being generated; retry in a few seconds",
+  }), "application/json; charset=utf-8", { ["Retry-After"] = "4" }
 end
 
 -- ── Tags ──────────────────────────────────────────────────────────────────────
@@ -410,9 +418,8 @@ end
 
 -- ── Full-resolution export ────────────────────────────────────────────────────
 -- POST /api/v1/images/:id/export
--- Enqueues a full-resolution JPEG export via the darktable bridge.
--- The bridge calls dt.new_format("jpeg"):write_image() which runs the complete
--- development pipeline.  Returns 202 immediately; poll GET /full to check when ready.
+-- Removes any stale export file, enqueues the bridge job, returns 202.
+-- The client should poll GET /full until it receives a 200.
 -- Requires scope: cache:refresh
 function M.trigger_export(req)
   local payload, s, b, ct = require_auth(req, "cache:refresh")
@@ -424,17 +431,17 @@ function M.trigger_export(req)
   local img = db.get_image(id)
   if not img then return err(404, "not_found", "image " .. id .. " not found") end
 
+  -- Remove stale export so the client can detect when the fresh one lands.
+  os.remove(export_path(id))
+
   local queued, qerr = enqueue_export(id)
-  if not queued then
-    return err(500, "queue_error", qerr)
-  end
+  if not queued then return err(500, "queue_error", qerr) end
 
   return 202, json.encode({
     status    = "accepted",
     image_id  = id,
     filename  = img.filename,
-    export    = export_path(id),
-    message   = "full-resolution export enqueued; poll GET /api/v1/images/" .. id .. "/full when ready",
+    message   = "export enqueued; poll GET /api/v1/images/" .. id .. "/full",
   }), "application/json; charset=utf-8"
 end
 
@@ -455,9 +462,10 @@ function M.get_full(req)
   local path = export_path(id)
   local f = io.open(path, "rb")
   if f then
-    local data = f:read("*a")
-    f:close()
-    return 200, data, "image/jpeg"
+    local data = f:read("*a"); f:close()
+    local stem = (img.filename or "export"):match("^(.+)%.[^.]+$") or (img.filename or "export")
+    local disposition = string.format('attachment; filename="%s.jpg"', stem)
+    return 200, data, "image/jpeg", { ["Content-Disposition"] = disposition }
   end
 
   -- Not yet exported — enqueue and tell the client to retry.