Split native Periscope (periscope/src) from inherited PinScope (periscope/dependency).

Keep validate.py and the finding engine as-is. AGPL LICENSE stays at the repo root.
Docker overlays dependency then src. Do not delete the inherited tree.

.github/workflows/ci.yml

@@ -14,20 +14,20 @@ jobs:
         with:
           python-version: "3.12"
           cache: pip
-      - run: pip install -r backend/requirements.txt pytest pytest-asyncio
+      - run: pip install -r periscope/dependency/backend/requirements.txt pytest pytest-asyncio
       - run: pytest tests/ -q
 
   frontend:
     runs-on: ubuntu-latest
-    defaults:
-      run:
-        working-directory: frontend
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
           node-version: 22
           cache: npm
-          cache-dependency-path: frontend/package-lock.json
+          cache-dependency-path: periscope/dependency/frontend/package-lock.json
+      - run: chmod +x scripts/materialize-frontend.sh && scripts/materialize-frontend.sh
       - run: npm ci
+        working-directory: .merge/frontend
       - run: npm run build
+        working-directory: .merge/frontend