feat: advanced features — dashboard, budgets, history, export

Backend:
- GET /api/v1/dashboard?month=YYYY-MM: KPIs, by_category, 6-month trend, budget alerts
- GET/POST/PUT/DELETE /api/v1/budgets: budget envelopes with spent_cents/remaining_cents
- POST /api/v1/budgets/rollover: copy budgets from M-1 to target month
- GET /api/v1/history?year=YYYY: monthly summary for the year
- GET /api/v1/export/csv|pdf?month=YYYY-MM: StreamingResponse exports (WeasyPrint PDF)
- New schemas: dashboard, budget, history
- Services: dashboard_service, budget_service
- Routers mounted in main.py

Frontend:
- DashboardPage: 4 KPI cards, PieChart (expenses by category), BarChart (6-month trend),
  month navigation, budget alert badges, CSV/PDF export buttons
- BudgetsPage: progress bars (green/orange/red), create/edit form, delete, rollover M-1
- HistoryPage: annual table with month click → dashboard, LineChart revenues/expenses
- CategoriesPage: list by type with create/edit/delete (was missing from Phase 2)
- TransactionsPage: added CSV/PDF export buttons
- App.tsx: full routing with ProtectedRoute + Layout for all authenticated pages
- New hooks: useDashboard, useBudgets (with mutations), useHistory
- API types + client updated for all new endpoints

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/hooks/useBudgets.ts

@@ -0,0 +1,49 @@
+import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
+import {
+  createBudget,
+  deleteBudget,
+  getBudgets,
+  rolloverBudgets,
+  updateBudget,
+} from "../api/client";
+import type { CreateBudgetPayload, UpdateBudgetPayload } from "../api/types";
+
+export function useBudgets(month?: string) {
+  return useQuery({
+    queryKey: ["budgets", month],
+    queryFn: () => getBudgets(month),
+  });
+}
+
+export function useCreateBudget() {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (payload: CreateBudgetPayload) => createBudget(payload),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ["budgets"] }),
+  });
+}
+
+export function useUpdateBudget() {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, payload }: { id: string; payload: UpdateBudgetPayload }) =>
+      updateBudget(id, payload),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ["budgets"] }),
+  });
+}
+
+export function useDeleteBudget() {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => deleteBudget(id),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ["budgets"] }),
+  });
+}
+
+export function useRolloverBudgets() {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (month: string) => rolloverBudgets(month),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ["budgets"] }),
+  });
+}

frontend/src/hooks/useDashboard.ts

@@ -0,0 +1,9 @@
+import { useQuery } from "@tanstack/react-query";
+import { getDashboard } from "../api/client";
+
+export function useDashboard(month?: string) {
+  return useQuery({
+    queryKey: ["dashboard", month],
+    queryFn: () => getDashboard(month),
+  });
+}

frontend/src/hooks/useHistory.ts

@@ -0,0 +1,9 @@
+import { useQuery } from "@tanstack/react-query";
+import { getHistory } from "../api/client";
+
+export function useHistory(year?: number) {
+  return useQuery({
+    queryKey: ["history", year],
+    queryFn: () => getHistory(year),
+  });
+}