ci: use node-go image instead of setup-go to reduce CI time

Switch all CI jobs (fmt, test, vet, staticcheck) to use the
pre-built git.thuanle.me/public/node-go container image, removing
the dynamic Go setup step from each job.

Closes #11

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -6,11 +6,10 @@ on:
 jobs:
   fmt:
     runs-on: linux
+    container:
+      image: git.thuanle.me/public/node-go
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-go@v5
-        with:
-          go-version-file: go.mod
       - run: |
           out=$(gofmt -l .)
           if [ -n "$out" ]; then
@@ -21,28 +20,25 @@ jobs:
 
   test:
     runs-on: linux
+    container:
+      image: git.thuanle.me/public/node-go
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-go@v5
-        with:
-          go-version-file: go.mod
       - run: go test ./...
 
   vet:
     runs-on: linux
+    container:
+      image: git.thuanle.me/public/node-go
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-go@v5
-        with:
-          go-version-file: go.mod
       - run: go vet ./...
 
   staticcheck:
     runs-on: linux
+    container:
+      image: git.thuanle.me/public/node-go
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-go@v5
-        with:
-          go-version-file: go.mod
       - run: go install honnef.co/go/tools/cmd/staticcheck@2025.1.1
       - run: $(go env GOPATH)/bin/staticcheck ./...