refactor: replace calloc with g_new0 for struct allocations

Migrate structure allocations from calloc to glibs g_new0 macro to
improve type safety and memory robustness.

* Type Safety: The macro takes the type name directly, ensuring the
  allocated size always matches the pointer type.
* Static Analysis: It guarantees a non-NULL return by aborting on
  failure, which silences -fanalyzer warnings regarding potential NULL
  pointer dereferences.
* Readability: Removes redundant sizeof() calls and is the glib way

src/config/account.c

@@ -59,7 +59,7 @@ account_new(gchar* name, gchar* jid, gchar* password, gchar* eval_password, gboo
             gchar* startscript, gchar* theme, gchar* tls_policy, gchar* auth_policy,
             gchar* client, int max_sessions)
 {
-    ProfAccount* new_account = calloc(1, sizeof(ProfAccount));
+    ProfAccount* new_account = g_new0(ProfAccount, 1);
 
     new_account->name = name;