Add an edit/delete manage screen to the Android app

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.

android/README.md

@@ -1,11 +1,14 @@
 # Gallery Upload — Android client
 
-Native uploader for the photogallery `POST /upload` endpoint. Pick or share a
-photo, add a caption and date, post. Credentials are entered once and sealed
-with a key held in the Android Keystore.
+Native uploader and manager for the photogallery server. Pick or share one or
+many photos, add caption/date/tags, and post. A **Manage** screen lists the
+published posts and edits their caption/date/tags or deletes them (to the
+server's trash) over the same `/api/*` endpoints the web `/manage` uses.
+Credentials are entered once and sealed with a key held in the Android Keystore.
 
 The server is not modified by this app. Everything it needs, it does client
-side.
+side; the management calls send no browser headers, so they pass the server's
+same-origin (CSRF) check as a non-browser client.
 
 ## Build