fix(metainfo): declare desktop and mobile device support (#4395)

The AppStream metainfo had no <requires>/<supports> relations, so software
stores such as Flathub listed Readest as "Desktop only". Readest is adaptive
and runs on desktop (keyboard/mouse) as well as phones and tablets (touch).

Declare a 360px display_length baseline plus keyboard, pointing and touch
controls so stores surface both Desktop and Mobile.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

data/metainfo/appdata.xml

@@ -59,6 +59,16 @@
 
   <launchable type="desktop-id">com.bilingify.readest.desktop</launchable>
 
+  <requires>
+    <display_length compare="ge">360</display_length>
+  </requires>
+
+  <supports>
+    <control>keyboard</control>
+    <control>pointing</control>
+    <control>touch</control>
+  </supports>
+
   <releases>
     <release version="0.11.2" date="2026-05-31">
       <description>