Add budget module: FastAPI backend + React frontend

Backend: FastAPI + PostgreSQL with models for accounts, transactions,
and categories. Auto-categorization from merchant patterns, token auth,
CRUD endpoints, and seed data for 16 categories and 4 bank accounts.

Frontend: Login, Dashboard (account balances + recent charges),
Transactions (full CRUD table with search/filter), Cash & Transfers
view. Dark theme with emerald/cyan accents, responsive layout.

Infrastructure: Updated docker-compose for backend + db services,
nginx proxy config for API routing, deploy workflow with secrets.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/api.ts

@@ -0,0 +1,69 @@
+import axios from 'axios';
+
+const api = axios.create({
+  baseURL: import.meta.env.VITE_API_URL || '/api/v1',
+});
+
+api.interceptors.request.use((config) => {
+  const token = localStorage.getItem('token');
+  if (token) config.headers.Authorization = `Bearer ${token}`;
+  return config;
+});
+
+api.interceptors.response.use(
+  (res) => res,
+  (err) => {
+    if (err.response?.status === 401) {
+      localStorage.removeItem('token');
+      window.location.href = '/login';
+    }
+    return Promise.reject(err);
+  },
+);
+
+export default api;
+
+export async function login(username: string, password: string) {
+  const form = new URLSearchParams();
+  form.append('username', username);
+  form.append('password', password);
+  const { data } = await api.post('/auth/login', form);
+  localStorage.setItem('token', data.access_token);
+  return data;
+}
+
+export interface Account {
+  id: number;
+  bank: string;
+  currency: string;
+  label: string;
+  balance: number;
+  updated_at: string;
+}
+
+export interface Category {
+  id: number;
+  name: string;
+  icon: string;
+  auto_match_patterns: string | null;
+}
+
+export interface Transaction {
+  id: number;
+  amount: number;
+  currency: string;
+  merchant: string;
+  city: string | null;
+  date: string;
+  card_type: string | null;
+  card_last4: string | null;
+  authorization_code: string | null;
+  reference: string | null;
+  transaction_type: string;
+  source: string;
+  bank: string;
+  notes: string | null;
+  category_id: number | null;
+  category: Category | null;
+  created_at: string;
+}