migrate from yarn 1 to pnpm

- switch root package manager to pnpm 10.33.4 via packageManager field
- add .npmrc with node-linker=hoisted for RN/Expo compatibility
- convert yarn resolutions to pnpm.overrides; pin psl@1.9.0 and @types/psl@1.1.1
  to keep types resolving under exports-aware resolution
- pin react-compiler-runtime and babel-plugin-react-compiler to real rc.3 (the
  deprecated "Wrong version name was published" tag would otherwise resolve)
- add pnpm.onlyBuiltDependencies allowlist for @sentry/cli, core-js-pure,
  esbuild, unrs-resolver
- regenerate pnpm-lock.yaml; delete yarn.lock; drop postinstall-postinstall
- update all workflows, Dockerfile, Dockerfile.embedr (root-level), Makefile,
  conductor.json; bskyembed/bskylink/bskyogcard/dev-env stay on yarn
- update docs (CLAUDE.md, docs/build.md, docs/testing.md, docs/localization.md,
  bskyweb/README.md, scripts/push-notification/README.md, BlueskyClip/README.md)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Dockerfile.embedr

@@ -29,11 +29,11 @@ RUN mkdir --parents $NVM_DIR && \
 RUN \. "$NVM_DIR/nvm.sh" && \
   nvm install $NODE_VERSION && \
   nvm use $NODE_VERSION && \
-  npm install --global yarn && \
-  yarn && \
+  npm install --global pnpm@10.33.4 yarn && \
+  pnpm install --frozen-lockfile && \
   cd bskyembed && yarn install --frozen-lockfile && cd .. && \
-  yarn intl:build && \
-  yarn build-embed
+  pnpm intl:build && \
+  pnpm build-embed
 
 # DEBUG
 RUN find ./bskyweb/embedr-static && find ./bskyweb/embedr-templates && find ./bskyembed/dist