Phase 4: Income API and page

- Add FrequencyCalculator static utility (all 9 frequency multipliers)
- Add IncomesController: list, create, update, delete, reorder
- Add Income DTOs with computed Monthly/Annually fields
- Add shared TypeScript types (IncomeDto, OutgoDto, BudgetDto, ShareDto, SummaryDto)
- Add API client with Bearer token injection via setTokenProvider
- Add FrequencySelect, MoneyDisplay, BudgetNav shared components
- Add Income page: sortable table with inline editing, add/delete rows, drag-to-reorder via dnd-kit
- Wire TokenWirer in App.tsx to keep API client in sync with auth state

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

src/Budget.Api/DTOs/IncomeDtos.cs

@@ -0,0 +1,19 @@
+using Budget.Api.Models;
+
+namespace Budget.Api.DTOs;
+
+public record IncomeDto(
+    Guid Id,
+    Guid BudgetId,
+    string Name,
+    Frequency Frequency,
+    decimal Amount,
+    decimal Monthly,
+    decimal Annually,
+    int SortOrder);
+
+public record CreateIncomeRequest(string Name, Frequency Frequency, decimal Amount);
+
+public record UpdateIncomeRequest(string Name, Frequency Frequency, decimal Amount);
+
+public record ReorderIncomesRequest(List<Guid> OrderedIds);