Proyecciones: clicking a month row opens that month in Budget

The clicked year/month now travel in the navigation state; Budget
seeds useBudget with them instead of always defaulting to today.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/hooks/useBudget.ts

@@ -16,11 +16,11 @@ import {
 
 /** All budget data hangs off the ['budget', ...] key family; every mutation
  * invalidates the family so projection, month detail and items stay in sync. */
-export function useBudget(initialYear: number) {
+export function useBudget(initialYear: number, initialMonth?: number) {
   const queryClient = useQueryClient();
   const [year, setYear] = useState(initialYear);
   const [selectedMonth, setSelectedMonth] = useState<number>(
-    new Date().getMonth() + 1,
+    initialMonth ?? new Date().getMonth() + 1,
   );
 
   const projectionQ = useQuery({

frontend/src/pages/Budget.tsx

@@ -22,6 +22,17 @@ const MAX_YEAR = 2030;
 
 export default function Budget() {
   const currentYear = Math.max(MIN_YEAR, new Date().getFullYear());
+  const location = useLocation();
+  const navigate = useNavigate();
+  // Proyecciones row clicks land here with the clicked period in the state.
+  const navState = location.state as
+    | { from?: string; year?: number; month?: number }
+    | null;
+  const cameFromProyecciones = navState?.from === 'proyecciones';
+  const initialYear =
+    navState?.year && navState.year >= MIN_YEAR && navState.year <= MAX_YEAR
+      ? navState.year
+      : currentYear;
   const {
     year,
     setYear,
@@ -35,12 +46,8 @@ export default function Budget() {
     updateItem,
     deleteItem,
     refresh,
-  } = useBudget(currentYear);
+  } = useBudget(initialYear, navState?.month);
   const queryClient = useQueryClient();
-  const location = useLocation();
-  const navigate = useNavigate();
-  const cameFromProyecciones =
-    (location.state as { from?: string } | null)?.from === 'proyecciones';
 
   const [subTab, setSubTab] = useState<'detail' | 'transactions'>('detail');
   const [txSearch, setTxSearch] = useState('');

frontend/src/pages/Proyecciones.tsx

@@ -99,7 +99,9 @@ export default function Proyecciones() {
               year={year}
               onSelectMonth={(m) => {
                 setSelectedMonth(m);
-                navigate('/budget', { state: { from: 'proyecciones' } });
+                navigate('/budget', {
+                  state: { from: 'proyecciones', year, month: m },
+                });
               }}
               onSaveOverride={async (month, value) => {
                 await saveBalanceOverride(year, month, value);