Add Expenses app

A UI based on [Budget Zen](https://github.com/BrunoBernardino/budgetzen-web) but slightly updated and adjusted for bewCloud. It also features a chart with available money and spent by budgets.

This is useful for envelope-based budgeting.

routes/api/expenses/auto-complete.tsx

@@ -0,0 +1,38 @@
+import { Handlers } from 'fresh/server.ts';
+
+import { FreshContextState } from '/lib/types.ts';
+import { getExpenseSuggestions } from '/lib/data/expenses.ts';
+
+interface Data {}
+
+export interface RequestBody {
+  name: string;
+}
+
+export interface ResponseBody {
+  success: boolean;
+  suggestions: string[];
+}
+
+export const handler: Handlers<Data, FreshContextState> = {
+  async POST(request, context) {
+    if (!context.state.user) {
+      return new Response('Unauthorized', { status: 401 });
+    }
+
+    const requestBody = await request.clone().json() as RequestBody;
+
+    if (!requestBody.name || requestBody.name.length < 2) {
+      return new Response('Bad request', { status: 400 });
+    }
+
+    const suggestions = await getExpenseSuggestions(
+      context.state.user.id,
+      requestBody.name,
+    );
+
+    const responseBody: ResponseBody = { success: true, suggestions };
+
+    return new Response(JSON.stringify(responseBody));
+  },
+};