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/.dockerignore

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+# Git
+.git
+.gitignore
+.github
+
+# Python
+__pycache__
+*.py[cod]
+*$py.class
+*.so
+.Python
+env/
+venv/
+.venv/
+ENV/
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+
+# Node
+node_modules/
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+.npm
+.eslintcache
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+.DS_Store
+
+# Testing
+.coverage
+htmlcov/
+.pytest_cache/
+.tox/
+
+# Documentation
+*.md
+docs/
+README.md
+PRD.MD
+CLAUDE.md
+*.log
+
+# Frontend build (built in Docker)
+frontend/dist/
+frontend/node_modules/
+
+# Development files
+.env
+*.local
+
+# Session files
+SESSION_*.md
+STEP_*.md
+PHASE_*.md
+DEBUG_*.md
+IMPLEMENTATION_*.md
+MIGRATION_*.md
+DECISIONS.md
+CACHING.md
+DAILY_SCAN_FEATURE.md
+FAST_FLIGHTS_TEST_REPORT.md
+WEB_APP_PRD.md
+RESUME_PROMPT.md