android: share a note with a group

The Share sheet lists groups after people, shows a group share as its name and
how many are in it, and shares through the FFI's ShareTarget.

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

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

@@ -67,7 +67,7 @@
     <string name="share_needs_server">Sharing is between people on a server. Link this phone in Sync to share notes.</string>
     <string name="share_none">Not shared with anyone yet.</string>
     <string name="share_everyone">Shared with everyone on this server.</string>
-    <string name="share_add">Add someone</string>
+    <string name="share_add">Add someone or a group</string>
     <string name="share_action">Share</string>
     <string name="share_remove">Stop sharing</string>
     <string name="share_can_view">Can view</string>
@@ -77,6 +77,10 @@
     <string name="share_by_can_edit">Shared by %1$s · you can edit the text</string>
     <string name="share_chip_shared">Shared</string>
     <string name="share_chip_by">From %1$s</string>
+    <plurals name="share_group_members">
+        <item quantity="one">Group · %d person</item>
+        <item quantity="other">Group · %d people</item>
+    </plurals>
 
     <!-- Attachments. A file is stored on the phone at once and uploaded on a later
          sync, so nothing here talks about the network. -->