Cleanup: Remove 7 obsolete Docker files — stale paths from pre-restructure

[mrveiss]

Problem

7 obsolete Docker files still exist on `Dev_new_gui` that reference old paths (`src/`, `autobot-vue/`, `backend/`, `main.py`) from before the codebase restructure. Listed as a deliverable in #1809.

Files to remove

All confirmed present on `origin/Dev_new_gui`:

1. `Dockerfile` (root)
2. `autobot-infrastructure/autobot-backend/docker/Dockerfile`
3. `autobot-infrastructure/shared/docker/docker-compose.yml`
4. `autobot-infrastructure/shared/docker/compose/docker-compose.yml`
5. `autobot-infrastructure/shared/docker/compose/docker-compose.hybrid.yml`
6. `autobot-infrastructure/shared/docker/ai-stack/Dockerfile`
7. `autobot-infrastructure/autobot-npu-worker/docker/Dockerfile`

Verification

```bash

All 7 exist on origin

git show origin/Dev_new_gui:Dockerfile >/dev/null 2>&1 && echo EXISTS
git show origin/Dev_new_gui:autobot-infrastructure/autobot-backend/docker/Dockerfile >/dev/null 2>&1 && echo EXISTS

... (all 7 confirmed)

```

Notes

• Playwright Docker files should be kept (still valid)
• NPU worker stays as VM — its Docker file is obsolete
• The new Docker stack lives in `docker/backend/`, `docker/frontend/`, `docker/slm/`

Discovered During

Reviewing Docker containerization work on #1809 (checklist item)

Impact

Severity: low — Confusing for contributors, no runtime impact. Dead code.

[mrveiss]

All 7 obsolete Docker files are already removed from Dev_new_gui (both local and origin). Likely cleaned up during #1809 Docker containerization work. Closing as resolved.