fix: replace setup-bun action with curl install for Gitea runner compatibility

oven-sh/setup-bun@v2 now requires node24 runtime, which Gitea Act
runner v0.2.11 does not support. Using direct curl install instead.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/deploy.yml

@@ -38,9 +38,9 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Setup Bun
-        uses: oven-sh/setup-bun@v2
-        with:
-          bun-version: latest
+        run: |
+          curl -fsSL https://bun.sh/install | bash
+          echo "$HOME/.bun/bin" >> $GITHUB_PATH
 
       - name: Install Dependencies
         run: bun install --frozen-lockfile