Update CI workflow to use pnpm for dependency management and upgrade Go version to 1.25.5

.gitea/workflows/ci.yml

@@ -16,9 +16,11 @@ jobs:
         uses: https://git.quad4.io/actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
         with:
           node-version: 22
-          cache: npm
+          cache: pnpm
+      - name: Enable corepack
+        run: corepack enable
       - name: Install dependencies
-        run: npm ci
+        run: pnpm install --frozen-lockfile
       - name: Frontend checks
         run: bash scripts/check.sh
       - name: Build frontend
@@ -43,7 +45,7 @@ jobs:
       - name: Setup Go
         uses: https://git.quad4.io/actions/setup-go@40f1582b2485089dde7abd97c1529aa768e1baff # v5
         with:
-          go-version: '1.25.4'
+          go-version: '1.25.5'
       - name: Build backend
         run: |
           mkdir -p bin