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/docker-compose.yml

@@ -0,0 +1,54 @@
+services:
+  # Backend API Server
+  backend:
+    build:
+      context: .
+      dockerfile: Dockerfile.backend
+    container_name: flight-radar-backend
+    restart: unless-stopped
+    ports:
+      - "8000:8000"
+    environment:
+      - PORT=8000
+      - DATABASE_PATH=/app/data/cache.db
+      - ALLOWED_ORIGINS=http://localhost,http://localhost:80,http://frontend
+    volumes:
+      - backend-data:/app/data
+      - ./cache.db:/app/cache.db:rw
+    networks:
+      - flight-radar-network
+    healthcheck:
+      test: ["CMD", "python", "-c", "import requests; requests.get('http://localhost:8000/health').raise_for_status()"]
+      interval: 30s
+      timeout: 3s
+      retries: 3
+      start_period: 10s
+
+  # Frontend UI
+  frontend:
+    build:
+      context: .
+      dockerfile: Dockerfile.frontend
+    container_name: flight-radar-frontend
+    restart: unless-stopped
+    ports:
+      - "80:80"
+    depends_on:
+      backend:
+        condition: service_healthy
+    networks:
+      - flight-radar-network
+    healthcheck:
+      test: ["CMD", "wget", "--quiet", "--tries=1", "--spider", "http://localhost/"]
+      interval: 30s
+      timeout: 3s
+      retries: 3
+      start_period: 5s
+
+networks:
+  flight-radar-network:
+    driver: bridge
+
+volumes:
+  backend-data:
+    driver: local