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/pages/Login.tsx

@@ -0,0 +1,89 @@
+import { useState } from 'react';
+import { useNavigate } from 'react-router-dom';
+import { Wallet, ArrowRight, AlertCircle } from 'lucide-react';
+
+import { login } from '../api';
+import { useAuth } from '../AuthContext';
+
+export default function Login() {
+  const [username, setUsername] = useState('');
+  const [password, setPassword] = useState('');
+  const [error, setError] = useState('');
+  const [loading, setLoading] = useState(false);
+  const navigate = useNavigate();
+  const { setAuthenticated } = useAuth();
+
+  const handleSubmit = async (e: React.FormEvent) => {
+    e.preventDefault();
+    setLoading(true);
+    setError('');
+    try {
+      await login(username, password);
+      setAuthenticated(true);
+      navigate('/');
+    } catch {
+      setError('Invalid credentials');
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  return (
+    <div className="min-h-screen bg-slate-950 flex items-center justify-center px-4">
+      <div className="w-full max-w-sm animate-fade-in">
+        <div className="flex items-center justify-center gap-2.5 mb-8">
+          <div className="w-10 h-10 rounded-lg bg-gradient-to-br from-emerald-400 to-cyan-400 flex items-center justify-center">
+            <Wallet className="w-6 h-6 text-slate-950" strokeWidth={2.5} />
+          </div>
+          <span className="text-2xl font-bold tracking-tight text-white">
+            Wealthy<span className="text-emerald-400">Smart</span>
+          </span>
+        </div>
+
+        <form onSubmit={handleSubmit} className="space-y-4">
+          <div>
+            <label className="block text-xs font-medium text-slate-400 mb-1.5 uppercase tracking-wider">
+              Username
+            </label>
+            <input
+              type="text"
+              value={username}
+              onChange={(e) => setUsername(e.target.value)}
+              className="w-full bg-slate-900 border border-slate-800 rounded-lg px-4 py-3 text-white placeholder-slate-600 focus:outline-none focus:border-emerald-500/50 focus:ring-1 focus:ring-emerald-500/20 transition-colors"
+              placeholder="Enter username"
+              autoFocus
+            />
+          </div>
+          <div>
+            <label className="block text-xs font-medium text-slate-400 mb-1.5 uppercase tracking-wider">
+              Password
+            </label>
+            <input
+              type="password"
+              value={password}
+              onChange={(e) => setPassword(e.target.value)}
+              className="w-full bg-slate-900 border border-slate-800 rounded-lg px-4 py-3 text-white placeholder-slate-600 focus:outline-none focus:border-emerald-500/50 focus:ring-1 focus:ring-emerald-500/20 transition-colors"
+              placeholder="Enter password"
+            />
+          </div>
+
+          {error && (
+            <div className="flex items-center gap-2 text-red-400 text-sm">
+              <AlertCircle className="w-4 h-4" />
+              {error}
+            </div>
+          )}
+
+          <button
+            type="submit"
+            disabled={loading}
+            className="w-full flex items-center justify-center gap-2 bg-emerald-500 hover:bg-emerald-400 disabled:opacity-50 text-slate-950 font-semibold px-6 py-3 rounded-lg transition-colors"
+          >
+            {loading ? 'Signing in...' : 'Sign in'}
+            {!loading && <ArrowRight className="w-4 h-4" />}
+          </button>
+        </form>
+      </div>
+    </div>
+  );
+}