Update CSP to allow external fonts, scripts, and add corresponding test coverage

public/js/script.js

@@ -1017,7 +1017,7 @@ if (headerModelButton) headerModelButton.addEventListener("click", (event) => {
 });
 saveGenerationSettingsBtn.addEventListener("click", () => { void saveGenerationSettings(); });
 roleplayNewPersonaBtn.addEventListener("click", closeRoleplayStarter);
-clearUserPersonaBtn.addEventListener("click", () => {
+if (clearUserPersonaBtn) clearUserPersonaBtn.addEventListener("click", () => {
     closeChatDrawer();
     void clearChatUserPersona();
 });