upload handling
- add app image parser/types/constants for ESP image header, extended
header, segments, and app description
- add shared binary read/write utilities and CRC32 helper
- add AppImageViewer component to inspect firmware metadata in UI
- improve upload UX: accept .bin only and show explicit error for ELF input
- prevent status alert timer race by clearing previous timeout before
setting a new one
- ignore .claude in .gitignore
kerms