ci: add bun setup for go generate in PR workflow

The miniapp package uses `//go:generate bun run` to build its frontend.
Without bun installed, `go generate ./...` fails in CI.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/pr.yml

@@ -16,6 +16,12 @@ jobs:
         with:
           go-version-file: go.mod
 
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@v2
+
+      - name: Install frontend deps
+        run: cd pkg/miniapp/frontend && bun install
+
       - name: Run go generate
         run: go generate ./...
 
@@ -55,6 +61,12 @@ jobs:
         with:
           go-version-file: go.mod
 
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@v2
+
+      - name: Install frontend deps
+        run: cd pkg/miniapp/frontend && bun install
+
       - name: Run go generate
         run: go generate ./...