refactor: extract Astrolabe to separate repository

Astrolabe has been extracted to its own repository at
github.com/cbcoutinho/astrolabe for independent releases.

Changes:
- Replace third_party/astrolabe/ directory with git submodule
- Remove astrolabe-ci.yml and appstore-build-publish.yml workflows
- Remove scripts/bump-astrolabe.sh
- Remove Astrolabe sections from bump-version.yml workflow
- Remove Astrolabe build steps from test.yml CI workflow
- Remove astrolabe volume mount from docker-compose.yml
- Simplify astrolabe install hook to always use app store
- Update CONTRIBUTING.md to reflect two-component monorepo

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/test.yml

@@ -48,23 +48,6 @@ jobs:
       ###### Required to build OIDC App ######
 
 
-      ###### Required to build Astrolabe App ######
-
-      - name: Set up Node.js for Astrolabe
-        uses: actions/setup-node@39370e3970a6d050c480ffad4ff0ed4d3fdee5af # v4.1.0
-        with:
-          node-version: '20'
-
-      - name: Build Astrolabe app
-        run: |
-          cd third_party/astrolabe
-          composer install --no-dev --optimize-autoloader
-          npm ci
-          npm run build
-
-      ###### Required to build Astrolabe App ######
-
-
       - name: Run docker compose
         uses: hoverkraft-tech/compose-action@4894d2492015c1774ee5a13a95b1072093087ec3 # v2.5.0
         with: