Add flight comparator web app with full scan pipeline

Full-stack flight price scanner built on fast-flights v3 (SOCS cookie bypass):

Backend (FastAPI + SQLite):
- REST API with rate limiting, Pydantic v2 validation, paginated responses
- Scan pipeline: resolves airports, queries every day in the window, saves
  individual flights + aggregate route stats to SQLite
- Background async scan processor with real-time progress tracking
- Airport search endpoint backed by OpenFlights dataset
- Daily scan window (all dates, not monthly samples)

Frontend (React 19 + TypeScript + Tailwind CSS v4):
- Dashboard with live scan status and recent scans
- Create scan form: country mode or specific airports (searchable dropdown)
- Scan detail page with expandable route rows showing individual flights
  (date, airline, departure, arrival, price) loaded on demand
- AirportSearch component with debounced live search and multi-select

Database:
- scans → routes → flights schema with FK cascade and auto-update triggers
- Migrations for schema evolution (relaxed country constraint)

Tests:
- 74 tests: unit + integration, isolated per-test SQLite DB
- Confirmed flight fixtures in tests/confirmed_flights.json (50 real flights,
  BDS→FMM Ryanair + BDS→DUS Eurowings, scraped Feb 2026)
- Integration tests parametrized from confirmed routes

Docker:
- Multi-stage builds, Compose orchestration, Nginx reverse proxy

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

flight-comparator/frontend/src/App.tsx

@@ -0,0 +1,28 @@
+import { BrowserRouter, Routes, Route } from 'react-router-dom';
+import Layout from './components/Layout';
+import Dashboard from './pages/Dashboard';
+import Scans from './pages/Scans';
+import ScanDetails from './pages/ScanDetails';
+import Airports from './pages/Airports';
+import Logs from './pages/Logs';
+import ErrorBoundary from './components/ErrorBoundary';
+
+function App() {
+  return (
+    <ErrorBoundary>
+      <BrowserRouter>
+        <Routes>
+          <Route path="/" element={<Layout />}>
+            <Route index element={<Dashboard />} />
+            <Route path="scans" element={<Scans />} />
+            <Route path="scans/:id" element={<ScanDetails />} />
+            <Route path="airports" element={<Airports />} />
+            <Route path="logs" element={<Logs />} />
+          </Route>
+        </Routes>
+      </BrowserRouter>
+    </ErrorBoundary>
+  );
+}
+
+export default App;