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>

backend/.containerignore

@@ -0,0 +1,48 @@
+# Build context = backend/. Keep it to source + manifests.
+# podman reads .containerignore; docker reads .dockerignore (a symlink of this
+# file lives next to it).
+
+# Virtualenvs / caches
+.venv/
+venv/
+env/
+__pycache__/
+**/__pycache__/
+*.py[cod]
+.mypy_cache/
+.ruff_cache/
+.pytest_cache/
+
+# Tests, coverage, dev artifacts
+tests/
+htmlcov/
+.coverage
+.coverage.*
+coverage.xml
+
+# Local databases — never bake user data into an image
+*.db
+*.db-shm
+*.db-wal
+*.db-journal
+
+# Secrets / local config
+.env
+.env.*
+!.env.example
+
+# Scraper page dumps and verification screenshots: REAL PERSONAL DATA from
+# Försäkringskassan. These must never enter an image layer.
+captures/
+debug/
+
+# Repo-level noise that is not part of this context anyway
+.git/
+.gitignore
+graphify-out/
+scripts/
+*.md
+!README.md
+Dockerfile
+.containerignore
+.dockerignore