build: add missing includes to header files

This change adds necessary `#include` directives that were previously
omitted in some header files. Without these includes, compilation
could fail or produce undefined behavior when the headers are used
in isolation (i.e., before their dependencies are included elsewhere).

Ensures better modularity and reliability of header usage.

src/xmpp/roster.h

@@ -10,6 +10,9 @@
 #ifndef XMPP_ROSTER_H
 #define XMPP_ROSTER_H
 
+#include "glib.h"
+#include <strophe.h>
+
 void roster_request(void);
 void roster_set_handler(xmpp_stanza_t* const stanza);
 void roster_result_handler(xmpp_stanza_t* const stanza);