Show on-device HTML UI mocks as firmware card previews.

Prefer media/preview.html over raster covers so catalog cards mirror each LVGL screen.

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

README.md

@@ -47,9 +47,11 @@ CYD_FIRMWARE_ROOT=C:\Users\dsx2016\Desktop\codes\cyd
 
 After rebuilding a project, run its `firmware\export_from_build.ps1`, then click **Refresh**.
 
-## Extending a firmware (media / docs)
+## Extending a firmware (HTML UI preview / docs)
 
-Create `meta.json` beside the `.bin` files:
+Preferred card preview: **`media/preview.html`** — HTML recreation of the on-device LVGL UI (320×240). Auto-detected if present.
+
+Optional `meta.json` beside the `.bin` files:
 
 ```json
 {
@@ -59,19 +61,18 @@ Create `meta.json` beside the `.bin` files:
   "description": "Longer detail text",
   "tags": ["pomodoro", "touch"],
   "media": {
-    "cover": "media/cover.webp",
-    "animation": "media/preview.gif",
+    "preview": "media/preview.html",
     "video": "media/demo.mp4",
     "docs": "docs/README.md"
   }
 }
 ```
 
-- Relative media paths are served via `/api/firmware/.../media/...` (only if the file exists).
+- Media paths are served via `/api/firmware/.../media/...` (only if the file exists).
 - `docs` may also be an `https://` URL.
 - `boardId` values: `esp32-2432s028` (active), `esp32-2432s024`, `esp32-3248s035`, `esp32-s3-touch` (UI reserved).
 
-Without `meta.json`, the catalog still works from `VERSION.txt`.
+Without `meta.json`, the catalog still works from `VERSION.txt` + auto `media/preview.html`.
 
 ## Public deploy (Docker + Caddy)