Add live POI tagging during wardrive

[datboip]

Summary

• Tap bottom bar during wardrive to drop GPS-tagged waypoints (auto-numbered POI 1, POI 2, etc.)
• CLI command wardrivepoi [label] for custom-named POIs over serial
• Standard GPX format with lat/lon/elevation/time/name
• Green flash confirmation on screen when POI is tagged
• Empty GPX files auto-cleaned on scan stop

Usage

1. Start a wardrive scan
2. Tap the bottom of the screen to mark a POI, or use CLI: wardrivepoi Starbucks
3. POIs saved to wardrive_poi_YYYYMMDD.gpx on SD card

Addresses #1058

Test plan

• Start wardrive → tap bottom bar → verify green flash + serial confirmation
• Verify GPX file created on SD with correct lat/lon/time/name
• wardrivepoi My Spot via CLI → verify custom label in GPX
• wardrivepoi with no args → verify auto-numbered label
• Stop wardrive → verify empty GPX files cleaned up
• Verify no interference with normal wardrive scanning

🤖 Generated with Claude Code