Attached images open full size and copy back out (#6198)

Scribe #6198 "An attached image can't be viewed large or copied back out".

Web and desktop: clicking an image in the editor opens it full size, with
Copy image (re-encoded to PNG, the one type every clipboard accepts),
Download and Close. Copy hides where the browser has no async clipboard,
such as a server reached over plain http; right-clicking the full-size
image still copies there.

Android: long-pressing an image in the editor copies it to the clipboard;
a tap still opens it full size in the phone's viewer. Opening and copying
share one hand-out that copies the file out of the blob store behind a
FileProvider URI.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

android/app/src/main/res/values/strings.xml

@@ -116,6 +116,10 @@
     <string name="attach_not_here">This file hasn\'t downloaded to this phone yet. Sync, then try again.</string>
     <string name="attach_no_app">No app on this phone opens this kind of file.</string>
     <string name="attach_open_failed">Couldn\'t open the file: %1$s</string>
+    <string name="attach_view">Open full size</string>
+    <string name="attach_copy">Copy image</string>
+    <string name="attach_copied">Image copied</string>
+    <string name="attach_copy_failed">Couldn\'t copy the image: %1$s</string>
     <string name="preview_remove">Remove link preview</string>
 
     <!-- Deleting for good is the only thing in the app that cannot be undone, so