Add container builds for the backend and the frontend

Backend: Alpine runtime without Chromium by default, opt-in Debian
scraper target with Playwright. Frontend: Vite build served by
nginx-unprivileged with the API upstream resolved at start.

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

frontend/.containerignore

@@ -0,0 +1,32 @@
+# Build context = frontend/. Everything the Vite build does not read stays out.
+
+node_modules/
+dist/
+coverage/
+test-results/
+playwright-report/
+.vite/
+.turbo/
+
+# Tests and E2E are gated in CI, not in the image build.
+tests/
+e2e/
+playwright.config.ts
+vitest.config.ts
+**/*.test.ts
+**/*.test.tsx
+
+# Local env / secrets
+.env
+.env.*
+!.env.example
+
+# Repo noise
+.git/
+.gitignore
+.DS_Store
+*.md
+out.js
+Dockerfile
+.containerignore
+.dockerignore