feat: rebuild internal MatAnyone2 workspace - #13

Summary

• add an internal webapp/workspace flow for MatAnyone2 testing
• support upload, clip range selection, anchor frame selection, interactive mask authoring, job queueing, and result review
• integrate SAM-driven annotation with MatAnyone2 inference/export paths
• add PowerShell entrypoints, smoke coverage, and webapp test coverage

Highlights

• unified workspace UI with clip/mask/refine/review steps
• processing-range and anchor-frame workflow for sub-clips
• export pipeline for foreground/alpha/png zip/prores outputs
• SQLite-backed jobs, worker loop, and restart-safe runtime layout
• local smoke runner and service scripts for internal testing

Verification

• D:\my_app\matanyone2\.worktrees\internal-webapp-ui-rebuild\.venv\Scripts\python.exe -m pytest tests\\webapp -q -> 86 passed
• D:\my_app\matanyone2\.worktrees\internal-webapp-ui-rebuild\.venv\Scripts\python.exe -m compileall matanyone2\\webapp scripts\\run_internal_webapp.py scripts\\run_internal_worker.py scripts\\smoke_internal_webapp.py -> passed