New BandConfig entries for 902, 1296, 2304, 3456, 5760 MHz:
- All beneficial humidity effect (like 10 GHz)
- Near-zero gaseous absorption and rain attenuation
- Ranges: 902 MHz typical 400 km, 5760 MHz typical 220 km
- Same seasonal curves as 10 GHz (ducting-driven)
BandConfig.band_options/0 generates dropdown options from configs.
All pages (path, rover, submit) use centralized band_options instead
of hardcoded lists. Map page already used BandConfig.all_bands().
10 GHz remains the default on all pages.