build: migrate from npm to pnpm with workspace catalogs

- Switch package manager to pnpm 10 via corepack
- Add pnpm-workspace.yaml with 54+ shared dependency catalogs
- Convert all workspace packages to catalog: and workspace:* protocols
- Upgrade Turborepo from 1.x to 2.8.12 (pipeline -> tasks)
- Upgrade apps/openpage-api from Next 15 to Next 16
- Update Docker, CI workflows, and GitHub Actions for pnpm
- Convert patch file to pnpm native format
- Replace deprecated next lint with standalone eslint
- Update all documentation references from npm to pnpm
- Fix stale dependabot config and documentation paths

.github/workflows/issue-assignee-check.yml

@@ -20,8 +20,6 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '18'
-          cache: npm
-
       - name: Install Octokit
         run: npm install @octokit/rest@18