chore: add a Taskfile facade over the existing commands

`task` with no arguments lists every runnable command. The Taskfile calls the
npm scripts, dotnet and docker compose. It does not duplicate their logic.
CI does not need `task`.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Taskfile.yml

@@ -0,0 +1,93 @@
+# ponytail: a thin façade over the npm scripts + dotnet + docker, NOT a second copy of
+# package.json. `task` (no args) lists everything runnable; the logic stays where it is —
+# `task ci` shells to scripts/ci-local.sh, which remains the gate. npm keeps working
+# exactly as before, and CI does not depend on `task` being installed.
+version: '3'
+
+tasks:
+  default:
+    silent: true
+    cmd: task --list
+
+  deps:
+    internal: true
+    status:
+      - test -d node_modules
+    cmd: npm ci
+
+  dev:
+    desc: Serve the SSP on :4200 (proxies /api to the backend)
+    deps: [deps]
+    cmd: npm start
+
+  dev:bp:
+    desc: Serve the behandelportal on :4201
+    deps: [deps]
+    cmd: npm run start:behandelportal
+
+  api:
+    desc: Run the backend on :5000 (Swagger at /swagger)
+    dir: backend
+    cmd: dotnet run --project src/BigRegister.Api
+
+  test:
+    desc: Run the frontend tests (both apps + both shared libraries)
+    deps: [deps]
+    cmd: npm test
+
+  test:api:
+    desc: Run the backend rule + endpoint tests (skips the OpenZaak integration tests)
+    dir: backend
+    # Same filter as scripts/ci-local.sh: the Integration tests need a running OpenZaak
+    # container (scripts/openzaak-ui-up.sh), so they are not part of the default gate.
+    cmd: dotnet test BigRegister.slnx --filter "Category!=Integration"
+
+  lint:
+    desc: Lint the frontend (no `any`, import/layer boundaries)
+    deps: [deps]
+    cmd: npm run lint
+
+  fmt:
+    desc: Format the frontend with prettier and the backend with dotnet format
+    deps: [deps]
+    cmds:
+      - npm run format
+      - dotnet format backend/BigRegister.slnx
+
+  build:
+    desc: Build both Angular apps
+    deps: [deps]
+    cmd: npm run build
+
+  ci:
+    desc: Run the CI gate locally before pushing (scripts/ci-local.sh)
+    deps: [deps]
+    cmd: npm run ci
+
+  e2e:
+    desc: Run the Playwright end-to-end tests (starts its own servers)
+    deps: [deps]
+    cmd: npm run e2e
+
+  sb:
+    desc: Run the SSP Storybook instance
+    deps: [deps]
+    cmd: npm run storybook
+
+  sb:bp:
+    desc: Run the behandelportal Storybook instance
+    deps: [deps]
+    cmd: npm run storybook:behandelportal
+
+  gen:api:
+    desc: Regenerate the typed API client from the backend OpenAPI document
+    deps: [deps]
+    cmd: npm run gen:api
+
+  up:
+    desc: Start both apps + the backend with docker compose
+    cmd: docker compose up
+
+  down:
+    desc: Stop the docker compose stack
+    cmd: docker compose down