chore: clean up repo organization

- Standardize on bun: remove package-lock.json, add packageManager field,
  gitignore non-bun lockfiles, fix stray npm install in android:build:clean
- Remove stale build logs and empty dirs (src-tauri/plugins, docs/tickets)
- Move android-dev.sh into scripts/
- Consolidate root docs into docs/ (docker/builder under docs/build/);
  move the architecture overview to docs/architecture/README.md
- Extract Requirements Specification from README into docs/requirements.md
  and slim README down to a project intro + docs index
- Fix internal references to the moved files

scripts/README.md

@@ -94,7 +94,7 @@ The traceability system is integrated with Gitea Actions CI/CD:
 
 For details, see:
 - [Traceability CI Guide](../docs/traceability-ci.md) - Full CI/CD documentation
-- [TRACES Quick Reference](../traces-quick-ref.md) - Quick guide for adding TRACES
+- [TRACES Quick Reference](../docs/traces-quick-ref.md) - Quick guide for adding TRACES
 
 ## Utility Scripts