Related to #600
- Add GPU field to Temperature model with edge, junction, and mem sensors
- Add amdgpu chip recognition to temperature parser
- Implement parseGPUTemps() to extract AMD GPU temperature data
- Update frontend TypeScript types to include GPU temperatures
- Display GPU temps in node table tooltip alongside CPU temps
- Set hasGPU flag when GPU data is available
This enables temperature monitoring for AMD GPUs (amdgpu sensors)
that was previously being collected via SSH but silently discarded
during parsing.