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

@@ -936,18 +936,14 @@ 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);
 
-    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_set_attribute(identity, "name", name_str->str);
+    g_string_free(name_str, TRUE);
     xmpp_stanza_add_child(query, identity);
     xmpp_stanza_release(identity);