ci: cache maven deps for deploy action

.github/workflows/deploy.yml

@@ -70,6 +70,14 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-pnpm-store-
 
+      - name: Cache Maven Deps
+        uses: actions/cache@v4
+        with:
+          path: $GITHUB_WORKSPACE/.m2/repository
+          key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
+          restore-keys: |
+            ${{ runner.os }}-maven-
+
       - name: Build backend
         working-directory: backend
         run: mvn --batch-mode --errors --fail-at-end --show-version --no-transfer-progress install