kordophoned: reorg: server impl in separate file, skeleton for conversations

kordophoned/include/net.buzzert.kordophonecd.Server.xml

@@ -4,5 +4,16 @@
         <method name="GetVersion">
             <arg type="s" name="version" direction="out" />
         </method>
+
+        <method name="GetConversations">
+            <arg type="aa{sv}" direction="out" name="conversations">
+            <annotation name="org.freedesktop.DBus.DocString" 
+                        value="Array of dictionaries. Each dictionary has keys:
+                                'id' (string): Unique identifier
+                                'title' (string): Display name
+                                'last_message' (string): Preview text
+                                'is_unread' (boolean): Unread status"/>
+            </arg>
+        </method>
     </interface>
 </node>