feat: Power consumption monitoring

[cursor]

Feature Description

Monitor power consumption of fans and provide statistics.

Hardware Addition

INA219/INA3221 current sensor:

• I2C interface
• Measure 12V rail current
• ~0.50€ per chip
• INA3221 can monitor 3 channels

Measurements

• 12V Rail Current
• 5V Rail Current (RGB LEDs)
• Total Power (Watts)
• Per-Fan Estimation (based on PWM)

Features

Real-time Monitoring

pico-fan-ctl power
# Output:
# 12V Rail: 1.2A (14.4W)
# 5V Rail: 0.8A (4.0W)
# Total: 18.4W
# Fan 1: ~2.4W

hwmon Integration

/sys/class/hwmon/hwmonX/
  in1_input    # 12V voltage
  curr1_input  # 12V current
  power1_input # 12V power (watts)

Statistics

• Min/Max/Average power
• Total energy consumed (kWh)
• Power per fan estimation
• Efficiency metrics

Use Cases

• Verify PSU capacity
• Detect power issues
• Energy monitoring
• Billing/cost calculation

Priority

Low - Nice to have