refactor: replace node with bun

.gitea/workflows/ci.yaml

@@ -1,4 +1,5 @@
 name: CI
+
 on:
   pull_request:
 
@@ -10,16 +11,15 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Setup Node.js
-        uses: actions/setup-node@v4
+      - uses: oven-sh/setup-bun@v2
         with:
-          node-version: ${{ inputs.node-version }}
+          bun-version-file: ".bun-version"
 
       - name: Install dependencies
-        run: npm install
+        run: bun install --frozen-lockfile
 
       - name: Run lint
-        run: npm run check:code
+        run: bun run check:code
 
       - name: Run spellcheck
-        run: npm run check:spell
+        run: bun run check:spell