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. Spoof the XEP-0115 capabilities node URI to
prevent service discovery/presence fingerprinting. These adjustments
reduce the client's attack surface by minimizing identifiable metadata.

src/xmpp/stanza.c

@@ -936,14 +936,18 @@ stanza_create_caps_query_element(xmpp_ctx_t* ctx)
 
     ProfAccount* account = accounts_get_account(session_get_account_name());
     gchar* client = account->client;
-    bool is_custom_client = client != NULL;
-
-    GString* name_str = g_string_new(is_custom_client ? client : "Pidgin");
-
     account_free(account);
 
-    xmpp_stanza_set_attribute(identity, "name", name_str->str);
-    g_string_free(name_str, TRUE);
+    auto_gchar gchar* name = g_strdup(client ? client : "Pidgin");
+
+    if (client) {
+        gchar* space = strchr(name, ' ');
+        if (space) {
+            *space = '\0';
+        }
+    }
+
+    xmpp_stanza_set_attribute(identity, "name", name);
     xmpp_stanza_add_child(query, identity);
     xmpp_stanza_release(identity);