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/profanity.c

@@ -253,7 +253,7 @@ _init(char* log_level, char* config_file, char* log_file, char* theme_name)
     log_stderr_init(PROF_LEVEL_ERROR);
 
     auto_gchar gchar* prof_version = prof_get_version();
-    log_info("Starting Profanity (%s)…", prof_version);
+    log_info("Starting CProof (%s)…", prof_version);
 
     chatlog_init();
     accounts_load();