Add battery and power consumption modeling

[NathanVRyver]

Feature

Request
Implement battery model and power consumption tracking for realistic flight time estimation.

Requirements

• Battery capacity and discharge curves
• Motor power consumption based on thrust
• Voltage sag under load
• Energy consumption metrics

Implementation

• Create src/power/ module
• Add battery configuration (capacity, cells, C-rating)
• Track instantaneous and cumulative power draw
• Calculate remaining flight time

Acceptance Criteria

• Accurate power consumption based on motor commands
• Battery voltage affects maximum thrust
• Flight terminates when battery depleted
• Power metrics in telemetry output