feat: German customer-facing desktop entry and AppStream metadata

Launcher shows "PC-Heini Fernwartung" with a plain-language description of
what the program does (remote support after the user's consent) instead of
the internal "HeiniRemote Agent — connects this machine to a HeiniRemote
server". English translations via Name[en]/xml:lang. Keywords make it
findable via PC-Heini, pcheini, Fernwartung, Fernhilfe, Support, HeiniRemote.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

de.pc_heini.HeiniRemoteAgent.metainfo.xml

@@ -3,14 +3,34 @@
   <id>de.pc_heini.HeiniRemoteAgent</id>
   <metadata_license>CC0-1.0</metadata_license>
   <project_license>proprietary</project_license>
-  <name>HeiniRemote Agent</name>
-  <summary>Remote maintenance agent for HeiniRemote</summary>
+  <name>PC-Heini Fernwartung</name>
+  <name xml:lang="en">PC-Heini Remote Support</name>
+  <summary>Fernwartung Ihres Computers durch PC-Heini</summary>
+  <summary xml:lang="en">Remote support for your computer by PC-Heini</summary>
   <description>
     <p>
-      Customer-side agent for HeiniRemote: Wayland screen capture and input
-      injection via xdg-desktop-portal, plus a PTY rescue console, streamed
-      over WebRTC to the HeiniRemote management console. Requires a HeiniRemote
-      server URL and device token (agent.toml).
+      Mit diesem Programm kann PC-Heini Ihren Computer aus der Ferne warten:
+      Bildschirm ansehen, Maus und Tastatur bedienen und bei Bedarf eine
+      Konsole nutzen. Nichts passiert ohne Ihre Zustimmung: Vor jeder Sitzung
+      fragt Ihr System, ob der Bildschirm freigegeben werden darf.
+    </p>
+    <p>
+      Die Verbindung ist Ende-zu-Ende verschlüsselt und läuft über den
+      Fernwartungsserver von PC-Heini. Das Programm läuft unauffällig im
+      Hintergrund und zeigt ein Symbol in der Leiste, solange es aktiv ist.
+    </p>
+  </description>
+  <description xml:lang="en">
+    <p>
+      This program lets PC-Heini service your computer remotely: view the
+      screen, operate mouse and keyboard and, if needed, use a console.
+      Nothing happens without your consent: before every session your system
+      asks whether the screen may be shared.
+    </p>
+    <p>
+      The connection is end-to-end encrypted and goes through PC-Heini's
+      remote support server. The program runs quietly in the background and
+      shows a tray icon while it is active.
     </p>
   </description>
   <launchable type="desktop-id">de.pc_heini.HeiniRemoteAgent.desktop</launchable>