CI: replace broken webpack/pages workflows with bun build check

The webpack.yml workflow ran `npx webpack` on a Vite project (no webpack
present), failing on every push/PR. static.yml uploaded the raw repo root
to GitHub Pages (not a real build; the app deploys via Vercel/Lovable) and
also failed. Replace both with a CI workflow that installs via bun
(bun.lockb is the maintained lockfile; package-lock.json is stale) and runs
the Vite build.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -0,0 +1,25 @@
+name: CI
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["main"]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+
+      - name: Install dependencies
+        run: bun install --frozen-lockfile
+
+      - name: Build
+        run: bun run build