feat: Add SQLite database integration for aircraft history and callsign enhancement

- Implement comprehensive database package with versioned migrations
- Add skyview-data CLI tool for managing aviation reference data
- Integrate database with merger for real-time aircraft history persistence
- Support OurAirports and OpenFlights data sources (runtime loading)
- Add systemd timer for automated database updates
- Fix transaction-based bulk loading for 2400% performance improvement
- Add callsign enhancement system with airline/airport lookups
- Update Debian packaging with database directory and permissions

Database features:
- Aircraft position history with configurable retention
- External aviation data loading (airlines, airports)
- Callsign parsing and enhancement
- API client for external lookups (OpenSky, etc.)
- Privacy mode for complete offline operation

CLI commands:
- skyview-data status: Show database statistics
- skyview-data update: Load aviation reference data
- skyview-data list: Show available data sources
- skyview-data clear: Remove specific data sources

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

.gitignore

@@ -36,4 +36,12 @@ Thumbs.db
 
 # Temporary files
 tmp/
-temp/
+temp/
+
+# Database files
+*.db
+*.db-shm
+*.db-wal
+*.sqlite
+*.sqlite3
+dev-skyview.db