A new Manage screen (reached from the Post screen) lists published posts with
thumbnails and lets you edit a post's caption, date and tags or delete it to the
server's trash, over the same /api/photos, /api/edit and /api/delete endpoints
the web /manage uses.
UploadClient gains listPhotos/editPost/deletePost/fetchThumbnail, parsing JSON
with the built-in org.json (no new dependency) and posting edits/deletes as
urlencoded forms. The app sends no Origin or Sec-Fetch-Site header, so it passes
the server's same-origin CSRF check as a non-browser client; Basic auth is
already attached on every request. UploadViewModel holds the manage state,
loads the list, fetches thumbnails in the background, and applies edits/deletes
optimistically.