chore(website): migrate to pnpm and enable minimum release age (#724)

## Summary

Migrates the `website/` subdirectory from Yarn 4 to pnpm 10.24.0 as part
of an org-wide supply-chain hardening effort. The Python root (`uv`) is
unchanged.

Enables a 24h minimum release age for third-party npm packages via
`pnpm-workspace.yaml` (with `@apify/*` and `@crawlee/*` excluded so
first-party releases stay fast), and mirrors the policy in
`renovate.json` via `internalChecksFilter=strict` plus a `packageRule`
that sets `minimumReleaseAge: 0 days` for the same scopes.

## Changes

- `website/package.json`: renamed to `apify-client-python-website`,
marked `private: true`, set `packageManager` to `pnpm@10.24.0`, rewrote
all script references from `yarn` to `pnpm`.
- `website/pnpm-workspace.yaml` (new): sets `minimumReleaseAge: 1440`
(minutes) with `@apify/*` and `@crawlee/*` excluded.
- `website/.npmrc` (new): enables hoisted node linker and workspace
package linking.
- `website/pnpm-lock.yaml` (new): generated from `pnpm install`.
- Removed Yarn artifacts: `website/yarn.lock`, `website/.yarnrc.yml`,
`website/.yarn/` (only contained `install-state.gz`; no `.yarn/patches/`
directory was present).
- `website/docusaurus.config.js`: renamed `future.experimental_faster`
to `future.faster` (required by Docusaurus 3.10).
- `.github/actions/pnpm-install/action.yml` (new): composite action
copied verbatim from `apify-client-js` for use by future CI workflows.
- `.github/workflows/_release_docs.yaml`: `git add website/yarn.lock` ->
`git add website/pnpm-lock.yaml`.
- `.github/workflows/manual_release_stable.yaml`: replaced inline `yarn
install` + `npx docusaurus` in the `version_docs` job with
`pnpm/action-setup`, `pnpm install --frozen-lockfile`, and `pnpm exec
docusaurus`. (Steps are inlined rather than calling
`./.github/actions/pnpm-install` because GitHub Actions does not support
`working-directory` on `uses:` steps and the composite expects to run
from the repo containing the lockfile.)
- `pyproject.toml`: `poe` tasks `update-docs-theme`, `build-docs`, and
`run-docs` now use `pnpm` instead of `yarn` / `corepack enable && yarn`.
- `renovate.json`: added `internalChecksFilter: "strict"` and a package
rule granting `@apify/*` / `@crawlee/*` a `0 days` minimum release age.
- `.gitignore`: dropped the now-obsolete `website/.yarn` entry.

Verified locally: `pnpm install`, `pnpm install --frozen-lockfile`, and
Docusaurus config validation all pass. A full `pnpm build` is gated by
the repo's Python docs pipeline (`pydoc-markdown`) which is invoked by
`uv run poe build-docs` in CI and was not re-run locally; the Docusaurus
config loads past the `future.faster` rename cleanly.

Rolls out the same pattern just applied to `apify-sdk-python`.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>