feat: support merged.bin, boot_app0, upload mode toggle + flash guide
- server.js: add boot_app0 field at 0xe000, raise file limit 8→32 MB
- index.html: add 병합/분리 mode toggle, boot_app0 drop zone, numbered split zones
- app.js: dynamic mode logic, remove hardcoded flashAddress 0x10000,
server now auto-selects 0x0 (merged) or 0x10000 (split)
- flash-guide.html: step-by-step Korean flash guide with file table,
method A/B walkthrough, flash_args explanation, troubleshooting
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
3a662affb6