docs: update all markdown files for v8.1.0 strict DI architecture

- CHANGELOG: add v8.1.0 entry (strict DI, composition roots, QMovie fix)
- README: update test badge (4021), source file count (106)
- ARCHITECTURE: add strict DI section, update lcd_device/builder descriptions
- DEVELOPMENT_STATUS: bump version, test counts, add roadmap item #36
- CLI_REFERENCE: merge config dir entries (~/.trcc/ is single location)
- DEVICE_TESTING: update test count from 4440 to 4021
- TECHNICAL_REFERENCE: rewrite file tree (add core/ files, remove deleted
  controllers.py/qt_app_mvc.py, add qt.py renderer, fix config path)
- CLAUDE.md/LEXICON.md/tests/README.md: update counts and terminology
- Remove obsolete USBLCD_PROTOCOL.md (content in TECHNICAL_REFERENCE.md)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>