feat: add deleteTransaction function

- Add deleteTransaction callback to hook
- Use filter to remove by id
- Save to AsyncStorage after delete

hooks/useTransactions.ts

@@ -34,10 +34,19 @@ export const useTransactions = () => {
     });
   }, []);
 
+  const deleteTransaction = useCallback((id: string) => {
+    setTransactions((prev) => {
+      const updated = prev.filter((t) => t.id !== id);
+      AsyncStorage.setItem(STORAGE_KEY, JSON.stringify(updated));
+      return updated;
+    });
+  }, []);
+
   return {
     transactions,
     loading,
     addTransaction,
+    deleteTransaction,
     refresh: loadTransactions,
   };
 };