WP-00: project skeleton with three-level test harness

Cargo workspace (domain, application, infrastructure, api), axum health endpoint
with SPA fallback, Vue 3 + Tailwind frontend, Vitest, Playwright, Makefile,
Gitea Actions CI and README.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -0,0 +1,39 @@
+name: CI
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  backend:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with: { components: rustfmt, clippy }
+      - uses: Swatinem/rust-cache@v2
+        with: { workspaces: backend }
+      - run: cd backend && cargo fmt --check && cargo clippy --workspace --all-targets -- -D warnings
+      - run: cd backend && cargo test --workspace
+
+  frontend:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with: { node-version: 22, cache: npm, cache-dependency-path: frontend/package-lock.json }
+      - run: cd frontend && npm ci
+      - run: cd frontend && npm run lint && npm run typecheck && npm test
+
+  ui:
+    runs-on: ubuntu-latest
+    needs: [backend, frontend]
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+        with: { workspaces: backend }
+      - uses: actions/setup-node@v4
+        with: { node-version: 22, cache: npm, cache-dependency-path: frontend/package-lock.json }
+      - run: cd frontend && npm ci && npx playwright install --with-deps chromium
+      - run: cd frontend && npm run test:ui