CI: Add explicite collections contract build to the coverage job

.github/workflows/codecov.yml

@@ -13,6 +13,9 @@ jobs:
         run: rustup update stable
       - name: Install cargo-llvm-cov
         uses: taiki-e/install-action@cargo-llvm-cov
+      # Explicitly build the collections contract first
+      - name: Build Collections Contract
+        run: cargo build --release -p phoenix-nft-collections --target wasm32-unknown-unknown
       - name: Generate code coverage
         run: cargo llvm-cov --all-features --workspace --codecov --output-path codecov.json
       - name: Upload coverage to Codecov