ci: fix zizmor ref-version-mismatch on actions/setup-node

zizmor v1.24.1의 `ref-version-mismatch` 룰이 pinned SHA와 주석 버전 불일치를
감지하여 경고 7건이 GitHub Actions Security job을 exit 13으로 실패시킴.

현재 상태:
- SHA `53b83947...` = actions/setup-node v6.3.0
- 주석 `# v6`은 현재 v6 floating tag가 가리키는 v6.4.0(`48b55a011bda`)을
  암시 → SHA와 주석이 다른 릴리즈를 가리키는 mismatch

해결 (zizmor 공식 권고 1순위: 주석을 실제 SHA에 맞춤):
- 7곳(.github/workflows/{ci,release,build-docs}.yml) 모두 `# v6` → `# v6.3.0`
- SHA는 유지하여 런타임 동작 변경 없음, 보안 감사만 통과하도록 최소 침습

관련 실패 run: solapi/solapi-nodejs#24647689822 (chore(beta): release 6.0.0-beta.4)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Palbahngmiyine

.github/workflows/build-docs.yaml

@@ -27,7 +27,7 @@ jobs:
         with:
           run_install: false
       - name: Setup Node.js
-        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6
+        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
         with:
           node-version: 18
       - name: Setup Pages

.github/workflows/ci.yml

@@ -34,7 +34,7 @@ jobs:
           run_install: false
 
       - name: Setup Node.js
-        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6
+        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
         with:
           node-version: 18
           cache: pnpm
@@ -66,7 +66,7 @@ jobs:
           run_install: false
 
       - name: Setup Node.js
-        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6
+        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
         with:
           node-version: ${{ matrix.node-version }}
           cache: pnpm
@@ -109,7 +109,7 @@ jobs:
           run_install: false
 
       - name: Setup Node.js
-        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6
+        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
         with:
           node-version: 18
           cache: pnpm

.github/workflows/release.yml

@@ -117,7 +117,7 @@ jobs:
           run_install: false
 
       - name: Setup Node.js
-        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6
+        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
         with:
           node-version: 18
 
@@ -189,7 +189,7 @@ jobs:
           run_install: false
 
       - name: Setup Node.js
-        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6
+        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
         with:
           node-version: 18
 
@@ -247,7 +247,7 @@ jobs:
           run_install: false
 
       - name: Setup Node.js
-        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6
+        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
         with:
           node-version: 24
           registry-url: https://registry.npmjs.org