fix(xmpp): obfuscate client identity in protocol exchanges

Modify version responses to return a generic client name and omit
version strings. Drop the "profanity." prefix from dynamically
generated JID resources. Clear the XEP-0115 capabilities node URI to
prevent service discovery fingerprinting. These adjustments reduce the
client's attack surface by minimizing identifiable metadata.

src/xmpp/jid.c

@@ -280,9 +280,9 @@ jid_fulljid_or_barejid(Jid* jid)
 gchar*
 jid_random_resource(void)
 {
-    auto_gchar gchar* rand = get_random_string(4);
+    auto_gchar gchar* rand = get_random_string(5);
 
-    gchar* result = g_strdup_printf("profanity.%s", rand);
+    gchar* result = g_strdup_printf("%s", rand);
 
     return result;
 }