feat: add flight tracking components and hooks

- Introduced FlightCard component for displaying flight information with animations.
- Added ScrollArea component for custom scroll behavior.
- Implemented StatusBar component to show flight count and loading status.
- Created useFlights hook for fetching and managing flight data based on city selection.
- Developed useSettings hook for managing user settings with local storage persistence.
- Added useTrailHistory hook for managing flight trail data.
- Defined City type and CITIES constant for city data management.
- Implemented flight utility functions for altitude and speed conversions.
- Created map styles for different visual representations.
- Added OpenSky API integration for fetching flight data.
- Implemented utility functions for class name merging.
- Configured TypeScript settings for the project.

.env.example

@@ -0,0 +1,15 @@
+# Environment Variables
+# Copy this file to .env.local and fill in your values.
+
+# ─── OpenSky Network API ──────────────────────────────────────────────────────
+#
+# OPTION 1 (Recommended): OAuth2 Client Credentials
+# For accounts created since mid-March 2025.
+# Go to https://opensky-network.org → Account → Create API Client
+OPENSKY_CLIENT_ID=
+OPENSKY_CLIENT_SECRET=
+
+# OPTION 2: Basic Auth (Legacy accounts only)
+# Deprecated — will be removed. Only works for accounts created before March 2025.
+# OPENSKY_USERNAME=
+# OPENSKY_PASSWORD=