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_date_resolver.py

@@ -0,0 +1,64 @@
+"""
+Smoke tests for date_resolver module.
+"""
+
+from datetime import date
+from dateutil.relativedelta import relativedelta
+import sys
+sys.path.insert(0, '..')
+
+from date_resolver import resolve_dates, detect_new_connections, SEARCH_WINDOW_MONTHS
+
+
+def test_resolve_dates_with_specific_date():
+    """Test that a specific date returns only that date."""
+    result = resolve_dates("2026-06-15", 6)
+    assert result == ["2026-06-15"]
+    print("✓ Specific date resolution works")
+
+
+def test_resolve_dates_seasonal():
+    """Test that seasonal mode generates one date per month."""
+    result = resolve_dates(None, 3)
+    assert len(result) == 3
+    # All should be valid date strings
+    for date_str in result:
+        assert len(date_str) == 10  # YYYY-MM-DD format
+        assert date_str.count('-') == 2
+    print(f"✓ Seasonal resolution works: {result}")
+
+
+def test_detect_new_connections():
+    """Test new connection detection logic."""
+    monthly_results = {
+        "2026-03": [
+            {"origin": "FRA", "destination": "JFK"},
+            {"origin": "MUC", "destination": "JFK"},
+        ],
+        "2026-04": [
+            {"origin": "FRA", "destination": "JFK"},
+            {"origin": "MUC", "destination": "JFK"},
+            {"origin": "BER", "destination": "JFK"},  # NEW
+        ],
+        "2026-05": [
+            {"origin": "FRA", "destination": "JFK"},
+            {"origin": "BER", "destination": "JFK"},
+            {"origin": "HAM", "destination": "JFK"},  # NEW
+        ],
+    }
+
+    new = detect_new_connections(monthly_results)
+    assert "BER->JFK" in new
+    assert new["BER->JFK"] == "2026-04"
+    assert "HAM->JFK" in new
+    assert new["HAM->JFK"] == "2026-05"
+    assert "FRA->JFK" not in new  # Was in first month
+    assert "MUC->JFK" not in new  # Was in first month
+    print(f"✓ New connection detection works: {new}")
+
+
+if __name__ == "__main__":
+    test_resolve_dates_with_specific_date()
+    test_resolve_dates_seasonal()
+    test_detect_new_connections()
+    print("\n✅ All date_resolver tests passed!")