Enable bounded GenAI content capture for Studio chat

[SushantGautam]

Summary

• pin Studio to simpleaudit==0.3.2
• pin embedded Open WebUI to v0.11.4.3-subpath and Compose to the matching image
• enable bounded, independently switchable GenAI content capture for the protected Studio OTLP receiver
• keep embedding vectors disabled by default and cap content at 2,000 characters
• document the capture settings and refresh the lockfile

Verification

• uv run pytest -m 'not embedded_hatchet' -q — 878 passed, 2 skipped, 4 deselected
• uv run pytest chat/tests/test_proxy.py -q — 19 passed
• uv run ruff check .
• docker compose config --quiet
• git diff --check