feat(deploy): add Docker image, static server, and CI workflows

One build artifact serves both a self-hosted subpath deploy and GitHub
Pages. CI runs the tests, typechecks, builds, and smoke-tests the image.

server.ts's traversal guard uses a separator-aware check
(resolved === root || resolved.startsWith(root + path.sep)) instead of
a bare startsWith(root), which would let a request resolving to
"/app/dist-evil/x" pass a check against root "/app/dist".

.github/workflows/ci.yml

@@ -0,0 +1,36 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+      - run: bun install --frozen-lockfile
+      - run: bun test
+      - run: bunx tsc --noEmit
+      - run: bun run build
+
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - run: docker build -t budget2 .
+      - name: Serve the image and check it responds
+        run: |
+          docker run -d --rm -p 3000:3000 --name budget2 budget2
+          for i in $(seq 1 30); do
+            if curl -fsS http://localhost:3000/ > /dev/null; then break; fi
+            sleep 1
+          done
+          curl -fsS http://localhost:3000/ | grep -q "Budget"
+          curl -fsS http://localhost:3000/sw.js > /dev/null
+          curl -fsS http://localhost:3000/manifest.webmanifest > /dev/null
+          docker stop budget2

.github/workflows/pages.yml

@@ -0,0 +1,46 @@
+name: Deploy to GitHub Pages
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+      - run: bun install --frozen-lockfile
+      - run: bun test
+      - name: Build for the Pages subpath
+        env:
+          BUN_PUBLIC_BASE_PATH: /${{ github.event.repository.name }}/
+          BUILD_VERSION: ${{ github.sha }}
+        run: bun run build
+      - name: Stop Pages from running the output through Jekyll
+        run: touch dist/.nojekyll
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: dist
+
+  deploy:
+    needs: build
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - id: deployment
+        uses: actions/deploy-pages@v4