docs: MkDocs scaffold, ADR-0001, README quickstart (refs #32)

Add mkdocs.yml (Material theme + nav), docs/index.md, and the first ADR
(docs/architecture/adr-0001-loose-coupling.md, Nygard template) recording
the loose-coupling stance from CLAUDE.md §8. Rewrite the README quickstart
to be accurate and reach a green local environment in under 10 minutes
(correct clone URL, .NET 10 + container-engine prereqs, `make ci` and the
compose smoke), and document building the docs site. Ignore .venv/ and site/.

Verified: `mkdocs build` succeeds; `make lint/build/unit` green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -41,31 +41,32 @@ For the architecture rationale, see [docs/PRD.md §3](docs/PRD.md) and [docs/arc
 
 **Prerequisites**
 
-- Docker Engine (or Docker Desktop) with Compose v2
-- ~8 GB free RAM, ~10 GB free disk
-- Bash or PowerShell
+- .NET 10 SDK (for `make lint/build/unit`)
+- A container engine with Compose v2 — Docker, or rootless Podman (see [docs/runbooks/ci.md](docs/runbooks/ci.md) for the Podman + Compose-provider setup)
+- `make`, `curl`, `git`
+- ~4 GB free RAM, ~5 GB free disk (grows as services land)
 
-**Bring the stack up**
+**Clone**
 
 ```bash
-git clone https://gitea.respellion.local/respellion/register-reference.git
-cd register-reference
-cp .env.example .env          # edit if you change ports
-docker compose -f infra/docker-compose.yml up -d
+git clone git@git.labs.respellion.tech:eho/register-referentie.git
+cd register-referentie
 ```
 
-Health checks should be green within ~3 minutes on a developer machine. If something fails, see [docs/runbooks/local-startup.md](docs/runbooks/local-startup.md).
+**Wired today (Iteration 0):** only the placeholder BFF exists so far. Get to green in under 10 minutes — run the full check gate, or just the running service:
 
-> **Wired today (Iteration 0):** only the placeholder BFF is in `infra/docker-compose.yml` so far. Bring it up and smoke-test its health endpoint:
->
-> ```bash
-> docker compose -f infra/docker-compose.yml up -d --build --wait
-> curl http://localhost:8080/health   # -> Healthy
-> ```
->
-> `--wait` exits non-zero unless the container reports healthy, so this doubles as the compose-up smoke test. The remaining services and the URLs below land in later slices.
+```bash
+make ci          # lint + build + unit + container smoke — the CI gate
+```
 
-**Default URLs**
+```bash
+docker compose -f infra/docker-compose.yml up -d --build --wait
+curl http://localhost:8080/health     # -> Healthy
+```
+
+`--wait` exits non-zero unless the container reports healthy, so it doubles as the compose-up smoke test. The remaining services and the URLs below land in later slices.
+
+**Target service URLs** *(most land in later slices)*
 
 | Service | URL |
 |---|---|
@@ -73,7 +74,7 @@ Health checks should be green within ~3 minutes on a developer machine. If somet
 | Openbaar register | http://localhost:4201 |
 | Behandel-portal | http://localhost:4202 |
 | Beheer-portal | http://localhost:4203 |
-| BFF | http://localhost:5000 |
+| BFF | http://localhost:8080 |
 | OpenZaak | http://localhost:8000 |
 | Open Notificaties | http://localhost:8001 |
 | Flowable | http://localhost:8080 |
@@ -82,10 +83,12 @@ Health checks should be green within ~3 minutes on a developer machine. If somet
 
 Test credentials, BSNs, and personas: see [docs/synthetic-data.md](docs/synthetic-data.md).
 
-**Re-seed synthetic data**
+**Build the docs site**
 
 ```bash
-./tools/seed.sh               # or pwsh ./tools/seed.ps1
+python3 -m venv .venv && .venv/bin/pip install mkdocs-material
+.venv/bin/mkdocs serve         # live preview at http://localhost:8000
+.venv/bin/mkdocs build         # static site in ./site
 ```
 
 ---