feat(satellites): Implement satellite pass tracking module

[arunderwood]

Summary

Add satellite pass predictions based on user location. Shows upcoming passes for amateur radio satellites (SO-50, ISS, RS-44, etc.).

Reference

See nextskip-project-plan.md for full specification.

Key Tasks

Backend

• Create satellites/ module structure
• Implement N2YO API client for pass predictions
• Implement Celestrak client for TLE data
• Integrate predict4java for local pass calculation
• Define active amateur satellite list
• Create SatellitePass model with scoring
• Add SatelliteEndpoint with @BrowserCallable

Frontend

• Create SatellitesCard component
• Add geolocation support (browser API or manual grid square)
• Display next 3 passes with countdown timers
• High score for imminent passes with good elevation

Dependencies

<dependency>
    <groupId>com.github.davidmoten</groupId>
    <artifactId>predict4java</artifactId>
    <version>1.3.1</version>
</dependency>

Environment Variables

N2YO_API_KEY=your-n2yo-api-key

Acceptance Criteria

• Shows passes for user's location
• Only shows passes with >20° max elevation
• Displays uplink/downlink frequencies
• TLEs refresh every 6 hours