add uv as a parallel option alongside pip

uv is presented as the recommended faster, standards-compliant drop-in;
pip stays the baseline/fallback. uv command syntax verified against
docs.astral.sh/uv before writing.

environments.md:
- new 'uv (optional, faster)' section: install from pyproject
  (uv pip install . / -e . / '.[dev]'), the uv sync managed-venv flow,
  and a note that uv.lock is local-only/gitignored (not committed)
- pinning subsection: pin direct deps in pyproject via == or git @ref,
  with a warning that this pins direct deps only — transitive deps still
  float at build time (documented tradeoff)
- uv equivalents added beside pip in the Local .venv and Docker tabs

deploy.md:
- 'Faster builds with uv' tip: uv-from-ghcr COPY, ENV UV_COMPILE_BYTECODE=1,
  uv pip install --system . (reads pyproject, no lock)
- layer-caching shows the uv variant beside the pip one
- checklist notes uv pip install + UV_COMPILE_BYTECODE; fix stray 'configs'
  plural -> 'config'

.gitignore: ignore uv.lock (local-only, never committed).

Verified in-browser; mkdocs build --strict clean (anchors resolve).

Signed-off-by: disqualifier <dev@disqualifier.me>

.gitignore

@@ -9,6 +9,7 @@ __pycache__/
 *.py[cod]
 .venv/
 venv/
+uv.lock
 
 # Playwright MCP run artifacts
 .playwright-mcp/