Repository Cleanup: Removal of Stale Documentation and Development Artifacts (QA)

This is an internal housekeeping change that removes 26 obsolete files from the frontend repository, including outdated design/implementation notes, leftover test screenshots, and superseded helper scripts. It contains no functional code changes and has no effect on the running application or any user-facing feature.

Over the course of earlier feature work, the repository accumulated a large amount of throwaway documentation (sorting and data-grid implementation notes, migration trackers, integration write-ups), captured browser-test screenshots, and one-off shell scripts. These artifacts were no longer accurate, duplicated information now held in the code itself or the proper documentation system, and added clutter that made the codebase harder to navigate. Removing them keeps the repository clean and reduces confusion for developers.

No impact on end users, clients, or application behavior — nothing that ships to the product was changed. The benefit is internal: a tidier codebase, less stale and potentially misleading documentation, and a smaller repository (roughly 5,600 lines of dead content removed).

Promotes the dev branch into qa, carrying the previously merged cleanup work (PR #342, branch cleanup-stale-markdown). The change is deletion-only (0 additions, ~5,599 deletions across 26 files):

• Removed stale markdown docs: data-grid component lists/usage, sorting implementation notes (multiple), PDF-viewer restructure notes, batch user flow, column-filters guide, rules/Filestack integration write-ups, department-edit example, drawer-actions migration status, unified mail update API notes, and the root README.md.
• Removed internal claude.readme/ tracker files (MEMORY.md, RULES_MODULE_TRACKER.md).
• Deleted a component-level doc src/components/ui/async-select-readme.md (the only file under src/; documentation only, no code).
• Removed 4 leftover Playwright test screenshots under .playwright-mcp/.
• Removed obsolete helper scripts implement-sorting-all-grids.sh and update_datagrids.sh.

Very low. The change only deletes documentation, images, and scripts; no application source code, configuration, or build logic was modified, so application behavior cannot regress. The residual risk is purely informational — a developer who relied on one of the removed notes will need to consult the code or current documentation instead. Mitigation: all deleted files remain recoverable from Git history if any reference is later needed.

Minimal QA required since no runtime behavior changed. Suggested checks: confirm the frontend still builds and the dev server starts cleanly after the deletions; verify the deleted root README.md and helper scripts were not referenced by any CI/build step or package script; smoke-test that the application loads normally in the QA environment.