docs(portals): ADR-0034 — Caddy serves the portals (refs #166)

Records the decision, the directive-order footgun that shapes the Caddyfiles, and
the measured cost (the images grew 75.7 MB → 90.6 MB). Also updates the three
frontend-decisions entries and the two other docs that named nginx.

docs/architecture/adr-0032-werkbak-live-refresh.md

@@ -18,7 +18,7 @@ Three forces shape the mechanism:
 
 - **Nothing notifies anyone.** The trigger lives in Flowable. The domain does not publish
   task events, and there is no bus between the domain and the BFF.
-- **The BFF is stateless** and sits behind each portal's nginx.
+- **The BFF is stateless** and sits behind each portal's reverse proxy.
 - **This is the repo's first live-updating view**, so the choice sets a precedent.
 
 ## Decision
@@ -40,7 +40,7 @@ werkbak is readable at all.
 Neither buys freshness here, because **nothing notifies the BFF either**:
 
 - **SSE** (`text/event-stream`) would mean a new streaming endpoint whose handler polls the
-  domain and forwards diffs — the same latency, plus connection lifecycle, nginx
+  domain and forwards diffs — the same latency, plus connection lifecycle, proxy
   buffering, and auth on a long-lived connection.
 - **WebSocket/SignalR** adds a dependency (CLAUDE.md §13) and makes the BFF stateful and
   sticky-session-bound. A genuine push path would *also* need the domain to publish task

docs/architecture/adr-0034-caddy-serves-the-portals.md

@@ -0,0 +1,103 @@
+# ADR-0034: The portals are served by Caddy, not nginx
+
+- **Status:** Accepted
+- **Date:** 2026-09-04
+- **Deciders:** Respellion engineering
+- **Slice:** _(none yet — raised directly alongside the Kubernetes deployment, ADR-0033)_
+
+## Context
+
+Each portal ships as one image that does two jobs: serve the built Angular app, and
+reverse-proxy *its own* BFF endpoint group so the browser calls a single origin (no CORS,
+and the DigiD/medewerker token rides along — ADR-0010, ADR-0013). Until now that was nginx
+with a hand-written `nginx.conf` per app.
+
+Two workarounds had accumulated around nginx's resolver, both for the same root cause:
+**nginx resolves a variable `proxy_pass` upstream itself**, using only the `resolver`
+directive, and never the search domains in `/etc/resolv.conf`.
+
+1. `resolver 127.0.0.11` (Docker's embedded DNS) is wrong on rootless podman, which uses a
+   network-specific aardvark address — so `apps/portal-nginx-resolver.sh` rewrote the
+   directive at container start by reading the pod's actual nameserver.
+2. On Kubernetes the bare `bff` name cannot resolve at all without the `svc.cluster.local`
+   search domain, so the same script gained a `BFF_HOST` override that the Helm chart set
+   per portal (ADR-0033).
+
+Both existed only to tell the proxy how to resolve one hostname.
+
+## Decision
+
+**Serve the portals with `caddy:2-alpine` and a small `Caddyfile` per app, replacing the
+nginx runtime stage, the four `nginx.conf` files, and the resolver workaround.**
+
+Caddy dials its upstream per request through Go's resolver, which reads
+`/etc/resolv.conf` — nameserver *and* search domains. So `reverse_proxy bff:8080` resolves
+correctly under Docker, rootless podman and Kubernetes with no per-engine configuration,
+and it still starts before the BFF exists and picks up its restarts (the property the
+variable `proxy_pass` was there to buy). `apps/portal-nginx-resolver.sh`, its unit test and
+the chart's `BFF_HOST` env are deleted.
+
+The Caddyfile uses `handle` blocks rather than a bare `try_files`:
+
+```
+handle /behandel/* { reverse_proxy bff:8080 }
+handle { root * /usr/share/caddy; try_files {path} /index.html; file_server }
+```
+
+`handle` blocks are mutually exclusive and matched most-specific-first. This matters:
+Caddy's default directive order puts rewrites (`try_files`) *before* `reverse_proxy`, so a
+top-level `try_files {path} /index.html` would rewrite every API path to `/index.html`
+before the proxy ever saw it — the SPA fallback would silently eat the API. The `handle`
+form makes the routing explicit instead of relying on directive-order trivia.
+
+`infra/test_portal_caddyfiles.py` (in `make unit`) asserts each portal proxies exactly its
+own endpoint groups and keeps the SPA fallback. The four files are near-identical, so a
+copy-paste slip is cheap to make and expensive to find: proxying another portal's group
+hands a browser an endpoint its token isn't for, and the failure surfaces as a 401 three
+services away.
+
+### Alternatives considered
+
+- **Keep nginx.** Zero migration, and it works — but the resolver workaround stays, and it
+  had already grown a second head for Kubernetes. Both heads are nginx-specific.
+- **Keep nginx, hard-code the FQDN.** Would need a different config per deployment target
+  (compose vs Kubernetes), which is exactly the fork the chart was written to avoid.
+- **Drop the proxy and use CORS.** Turns the same-origin design (ADR-0010) inside out:
+  CORS preflights, an explicit origin allowlist in the BFF, and a token attached
+  cross-origin. Not a serving decision — an architectural regression.
+- **Kubernetes Ingress in front of the portals.** Solves nothing about compose, adds a
+  controller, and the portals would still need something to serve static files.
+
+- ponytail ceiling: plain HTTP on `:80`, no compression, no cache headers beyond Caddy's
+  defaults, and Caddy's automatic HTTPS deliberately unused (there is no hostname to get a
+  certificate for). Upgrade path: `encode zstd gzip` and a cache policy for immutable
+  Angular bundles; a real hostname makes TLS a one-line `Caddyfile` change, which is the
+  main reason this is worth having in place.
+
+## Consequences
+
+**Positive**
+
+- One resolver behaviour across compose, podman and Kubernetes; a script, a unit test and a
+  chart env var are deleted rather than maintained.
+- The images gain `curl` for free (the alpine nginx image had only busybox `wget`), which
+  the compose healthchecks can use.
+- Routing intent is readable: one `handle` block per endpoint group, one for the app.
+- TLS later is a one-line change instead of a new component.
+
+**Negative / costs**
+
+- A new runtime dependency in four images (CLAUDE.md §13): Caddy replaces nginx rather than
+  joining it, so the count is unchanged, but it is a less familiar config language for
+  anyone who has only read nginx configs.
+- The images grew: 90.6 MB against nginx's 75.7 MB, because `caddy:2-alpine` carries a
+  bigger static binary than nginx's. Measured, not estimated.
+- Caddy's directive-order rule is a genuine footgun (see above); the `handle` form and the
+  Caddyfile comments exist to keep the next person out of it.
+- Any operational note that says "the portal's nginx" is now wrong; the ones in `docs/` were
+  updated with this ADR.
+
+## Coupling rules touched (CLAUDE.md §8)
+
+None. §8.3 is unchanged and unchanged in kind: the portals still talk only to the BFF, and
+the proxy is still the thing that makes that same-origin.