Extract helper functions to reduce complexity in functions with
complexity 10-15:
- packet.ex: Extract add_symbol_data/2
Moves symbol data extraction into separate function
Reduces complexity from 10 to 9
- mobile_channel.ex: Extract bounds validation helpers
Creates all_numeric?/4, valid_latitudes?/2, valid_longitudes?/2
Moves complex boolean conditions into readable helper functions
Reduces complexity from 15 to within limits
- historical_loader.ex: Extract packet_has_valid_coordinates?/1
Moves coordinate validation logic with multiple conditions
Reduces complexity from 15 to within limits
Fixes 3 more Credo cyclomatic complexity issues.