v0.9.4: security release

Closes three coordinated-disclosure advisories in the Docker server's
egress controls and untrusted-config gate.

  GHSA-f77g-77vp-r96v  blind SSRF via the robots.txt fetch
  GHSA-wh5w-hmj3-vgg7  SSRF with response disclosure via link preview
  GHSA-5w5p-vcv6-mm3f  untrusted-config gate bypass leaking env vars

Also adds PruningContentFilterLXML, about 10x faster pruning, now the
default. No breaking changes.

docs: release notes, changelog, README, and security credits for v0.9.4

Bump the version to 0.9.4 and add the v0.9.4 fixes to SECURITY.md.

v0.9.3: security release

Closes five coordinated-disclosure advisories in the PDF processing path
and the Docker Playground UI.

  GHSA-xpp7-j28w-2gvx  arbitrary file write via PDF image-write fields
  GHSA-q5rj-45vw-vp2g  SSRF, PDF fetch followed redirects unvalidated
  GHSA-v2rm-hvrj-2x9q  DoS, unbounded PDF size and page count
  GHSA-7g3g-vhm6-79f3  XSS, PDF text unescaped into cleaned_html
  GHSA-m446-hp3q-qfxp  DOM XSS in the playground, API token theft

No new features. No breaking changes.

docs: release notes, changelog, README, and security credits for v0.9.3

Release v0.9.2: Maintenance Bug Fixes

- Dispatcher: clean up leaked tasks/pages on streaming crawl close (#2071)
- Docker: Playground config 400, Monitor WebSocket 500, headless shell (#2059, #2060, #2067)
- GPU: ENABLE_GPU=true CUDA toolkit build fix (#2020)

Merge pull request #2077 from unclecode/release/v0.9.2

release: Crawl4AI v0.9.2

Release v0.9.1: Bug Fixes & PruningContentFilter Whitelist

- PruningContentFilter preserve_classes/preserve_tags whitelist
- 12 bug fixes across Docker, browser, core, and extraction
- lxml ceiling widened to allow 6.x

Merge pull request #2061 from unclecode/release/v0.9.1

release: Crawl4AI v0.9.1

v0.9.0 - secure-by-default Docker server (breaking); download path-tr…

…aversal, stream SSRF, extra_args RCE fixes

v0.9.0 - secure-by-default Docker server (breaking); download path-tr…

…aversal, stream SSRF, extra_args RCE fixes