refactor: enhance email scheduling functionality and improve error handling

- Added a new mutation to cancel scheduled emails, ensuring only pending emails can be canceled.
- Updated the current user query to use type casting for better type safety.
- Improved the handling of email status queries to skip execution when no email IDs are present.
- Refactored error checking for template queries to streamline the code and remove unused variables.
- Enhanced user feedback for authentication requirements when sending notifications.

packages/backend/convex/email.ts

@@ -162,6 +162,29 @@ export const enfileirarEmail = mutation({
   },
 });
 
+/**
+ * Cancelar agendamento de email
+ */
+export const cancelarAgendamentoEmail = mutation({
+  args: {
+    emailId: v.id("notificacoesEmail"),
+  },
+  handler: async (ctx, args) => {
+    const email = await ctx.db.get(args.emailId);
+    if (!email) {
+      return { sucesso: false, erro: "Email não encontrado" };
+    }
+
+    if (email.status !== "pendente") {
+      return { sucesso: false, erro: "Apenas emails pendentes podem ser cancelados" };
+    }
+
+    // Remove o email da fila
+    await ctx.db.delete(args.emailId);
+    return { sucesso: true };
+  },
+});
+
 /**
  * Enviar email usando template
  */