Update aircraft legend to show real ADS-B categories and implement pure Go ICAO country lookup

- Replace imaginary aircraft types (Commercial/Cargo/GA) with actual ADS-B emitter categories
- Add proper weight-based classifications: Light <7000kg, Medium 7000-34000kg, etc.
- Replace SQLite-based ICAO lookup with pure Go implementation using slice of allocations
- Remove SQLite dependency completely for simpler architecture
- Add comprehensive ICAO address allocations based on ICAO Document 8585
- Implement efficient linear search through sorted allocations by start address

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

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

go.sum

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