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/tests/test_formatter.py

@@ -0,0 +1,23 @@
+"""
+Smoke tests for formatter module.
+"""
+
+import sys
+sys.path.insert(0, '..')
+
+from formatter import format_duration
+
+
+def test_format_duration():
+    """Test duration formatting."""
+    assert format_duration(0) == "—"
+    assert format_duration(60) == "1h"
+    assert format_duration(90) == "1h 30m"
+    assert format_duration(570) == "9h 30m"
+    assert format_duration(615) == "10h 15m"
+    print("✓ Duration formatting works")
+
+
+if __name__ == "__main__":
+    test_format_duration()
+    print("\n✅ All formatter tests passed!")