Mutation feedback: toasts on transaction save/delete, confirm override clear

Transaction create/update/delete now confirm success or failure with a
toast (UX-01); save failures always show a user-visible message instead
of console-only (FE-06, with a typed error guard replacing the any
cast). Clearing a balance override — which recalculates every following
month — now requires confirmation like the other destructive actions
(UX-15).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/components/TransactionList.tsx

@@ -11,6 +11,8 @@ import {
   Banknote,
 } from 'lucide-react';
 
+import { toast } from 'sonner';
+
 import api, { type Transaction } from '@/lib/api';
 import TransactionModal from './TransactionModal';
 import ConfirmDialog from './ConfirmDialog';
@@ -66,8 +68,11 @@ export default function TransactionList({
     setDeleting(true);
     try {
       await api.delete(`/transactions/${deleteId}`);
+      toast.success('Transacción eliminada');
       setDeleteId(null);
       onRefresh();
+    } catch {
+      toast.error('No se pudo eliminar la transacción');
     } finally {
       setDeleting(false);
     }

frontend/src/components/TransactionModal.tsx

@@ -1,4 +1,6 @@
 import { useEffect, useState } from 'react';
+import { toast } from 'sonner';
+
 import api, { type Category, type Transaction } from '@/lib/api';
 import { formatLocalDatetime } from '@/lib/format';
 import { Button } from '@/components/ui/button';
@@ -92,12 +94,18 @@ export default function TransactionModal({ transaction, source, onClose, onSaved
       } else {
         await api.post('/transactions/', payload);
       }
+      toast.success(transaction ? 'Transacción actualizada' : 'Transacción creada');
       onSaved();
       onClose();
-    } catch (err: any) {
-      if (err.response?.status === 409) {
+    } catch (err) {
+      const status =
+        err && typeof err === 'object' && 'response' in err
+          ? (err as { response: { status: number } }).response.status
+          : null;
+      if (status === 409) {
         setError('Duplicate transaction: a transaction with this reference already exists.');
       } else {
+        setError('No se pudo guardar la transacción.');
         console.error(err);
       }
     } finally {

frontend/src/components/budget/YearlyOverview.tsx

@@ -1,3 +1,4 @@
+import ConfirmDialog from '@/components/ConfirmDialog';
 import { useState, useRef, useEffect } from 'react';
 import { Pencil } from 'lucide-react';
 
@@ -42,6 +43,7 @@ export default function YearlyOverview({
   const currentMonth = new Date().getMonth() + 1;
   const currentYear = new Date().getFullYear();
   const [editingMonth, setEditingMonth] = useState<number | null>(null);
+  const [confirmClearMonth, setConfirmClearMonth] = useState<number | null>(null);
   const [editValue, setEditValue] = useState('');
   const inputRef = useRef<HTMLInputElement>(null);
 
@@ -61,7 +63,16 @@ export default function YearlyOverview({
     if (editingMonth === null) return;
     const trimmed = editValue.trim();
     if (trimmed === '') {
-      await onClearOverride(editingMonth);
+      // Clearing an override is destructive — confirm first (it changes the
+      // cumulative chain for every following month).
+      const hadOverride = months.find(
+        (m) => m.month === editingMonth,
+      )?.balance_overridden;
+      if (hadOverride) {
+        setConfirmClearMonth(editingMonth);
+        setEditingMonth(null);
+        return;
+      }
     } else {
       const num = parseFloat(trimmed);
       if (!isNaN(num)) {
@@ -71,6 +82,12 @@ export default function YearlyOverview({
     setEditingMonth(null);
   };
 
+  const handleConfirmClear = async () => {
+    if (confirmClearMonth === null) return;
+    await onClearOverride(confirmClearMonth);
+    setConfirmClearMonth(null);
+  };
+
   const handleKeyDown = (e: React.KeyboardEvent) => {
     if (e.key === 'Enter') {
       handleSave();
@@ -202,6 +219,15 @@ export default function YearlyOverview({
           })}
         </TableBody>
       </Table>
+      {confirmClearMonth !== null && (
+        <ConfirmDialog
+          title="Eliminar ajuste de balance"
+          message={`El balance de ${MONTH_NAMES[confirmClearMonth] ?? confirmClearMonth} volverá al valor calculado y los meses siguientes se recalcularán.`}
+          confirmLabel="Eliminar ajuste"
+          onConfirm={handleConfirmClear}
+          onCancel={() => setConfirmClearMonth(null)}
+        />
+      )}
     </div>
   );
 }