ci: use go-react image toolchains instead of setup-go/setup-node

On the go-react runner image, npm/node/go already work (npm ci succeeds),
but the setup-go/setup-node actions install tool-cache binaries that can't
execute on this runner (node/22.22.3/x64: "cannot execute"), failing the
jobs in their post steps. Drop those actions and use the image's built-in
toolchains; also reduces flaky github.com action clones.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitea/workflows/build-dev.yaml

@@ -7,8 +7,6 @@ on:
   workflow_dispatch:
 
 env:
-  GO_VERSION: "1.25"
-  NODE_VERSION: "22"
   BINARY_NAME: remoterig
 
 jobs:
@@ -18,15 +16,12 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Setup Go
-        uses: actions/setup-go@v5
-        with:
-          go-version: ${{ env.GO_VERSION }}
-
-      - name: Setup Node
-        uses: actions/setup-node@v4
-        with:
-          node-version: ${{ env.NODE_VERSION }}
+      # The go-react image ships Go + Node, so no setup-go/setup-node:
+      # those download tool-cache binaries that don't run on this runner.
+      - name: Toolchain versions
+        run: |
+          go version
+          node --version
 
       - name: Build React frontend
         run: |