feat: add CI, Docker, auth, typed API client, shiki code blocks, e2e tests

- CI: GitHub Actions (bun 1.3.14, lint/typecheck/test/build/format gates)
- Docker: multi-stage standalone build + .dockerignore (next.config output=standalone)
- Auth: better-auth server (memory adapter, drizzle-swap-ready) + react client
  + /api/auth/[...all] route handler
- API: /api/health + /api/openapi routes, openapi-typescript codegen to
  types/api.ts, typed openapi-fetch client (lib/api, lib/http)
- Shiki: server-side CodeBlock component (escaped HTML)
- E2E: playwright home + health specs on dedicated :3100 (chromium 1243
  installed from GCS after CDN timeout)
- Dev: allow 127.0.0.1/localhost dev origins (HMR for local tooling)

playwright.config.ts

@@ -8,7 +8,7 @@ export default defineConfig({
   workers: process.env.CI ? 1 : undefined,
   reporter: "html",
   use: {
-    baseURL: "http://127.0.0.1:3000",
+    baseURL: "http://127.0.0.1:3100",
     trace: "on-first-retry",
   },
   projects: [
@@ -18,8 +18,8 @@ export default defineConfig({
     },
   ],
   webServer: {
-    command: "bun run dev",
-    url: "http://127.0.0.1:3000",
+    command: "PORT=3100 bun run dev",
+    url: "http://127.0.0.1:3100",
     reuseExistingServer: !process.env.CI,
     timeout: 120_000,
   },