revert: remove actions/cache - runner v0.3.1 doesn't set ACTIONS_CACHE_URL in Docker mode

Keeping Docker layer caching (--cache-from/--cache-to) as the
effective optimization. actions/cache needs runner update.

.gitea/workflows/pr.yml

@@ -22,21 +22,6 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v4
 
-      - name: Compute dependency cache key
-        id: npm-key
-        run: |
-          echo "hash=$(sha256sum package-lock.json | cut -d' ' -f1)" >> $GITHUB_OUTPUT
-
-      - name: Cache node_modules
-        uses: actions/cache@v3
-        with:
-          path: |
-            node_modules
-            ~/.npm
-          key: npm-${{ runner.os }}-${{ steps.npm-key.outputs.hash }}
-          restore-keys: |
-            npm-${{ runner.os }}-
-
       - name: Install dependencies
         run: npm ci --legacy-peer-deps
 
@@ -61,21 +46,6 @@ jobs:
 
       # Required for acceptance tests - they import prisma via @/ path alias
       # and @cucumber/cucumber for cucumber-e2e tests
-      - name: Compute dependency cache key
-        id: npm-key
-        run: |
-          echo "hash=$(sha256sum package-lock.json | cut -d' ' -f1)" >> $GITHUB_OUTPUT
-
-      - name: Cache node_modules
-        uses: actions/cache@v3
-        with:
-          path: |
-            node_modules
-            ~/.npm
-          key: npm-${{ runner.os }}-${{ steps.npm-key.outputs.hash }}
-          restore-keys: |
-            npm-${{ runner.os }}-
-
       - name: Install dependencies
         run: npm ci --legacy-peer-deps