fix(infra): engine-portable portal nginx resolver (closes #96) (#97)

## What & why

Closes #96. The portal nginx configs hardcode `resolver 127.0.0.11` (Docker's embedded DNS) for their variable `proxy_pass` to the BFF, so on rootless **podman** (network-specific aardvark DNS) every proxied call 502'd — the portals loaded and login worked, but no in-app data flowed.

Add a shared `/docker-entrypoint.d` hook (`apps/portal-nginx-resolver.sh`, wired into all three portal Dockerfiles) that rewrites the resolver from the container's own `/etc/resolv.conf` at startup: a **no-op on Docker** (nameserver *is* 127.0.0.11) and **correct on podman** (rewrites to e.g. 10.89.0.1). nginx.conf is unchanged (the hardcoded value is the substitution anchor).

## How verified

Built the behandel image and ran it on the compose network under podman: the hook rewrote the config to `resolver 10.89.0.1`, and `GET /behandel/werkbak` proxied to the BFF returning **401** (auth), not 502. On Docker the nameserver is 127.0.0.11 so the substitution is a no-op and CI/e2e behaviour is unchanged.

Reviewed-on: #97

apps/behandel/Dockerfile

@@ -19,5 +19,9 @@ COPY --from=build /src/dist/apps/behandel/browser /usr/share/nginx/html
 # Compose-time OIDC config: the browser (Playwright, on the compose network) reaches Keycloak by
 # service name, so the token issuer matches the BFF's medewerker authority (host-consistent, ADR-0013).
 RUN printf '{ "authority": "http://keycloak:8080/realms/medewerker" }\n' > /usr/share/nginx/html/config.json
+# Make the reverse-proxy resolver engine-portable (Docker 127.0.0.11 vs podman aardvark); runs from
+# the nginx image's /docker-entrypoint.d before nginx starts.
+COPY apps/portal-nginx-resolver.sh /docker-entrypoint.d/40-resolver.sh
+RUN chmod +x /docker-entrypoint.d/40-resolver.sh
 
 EXPOSE 80

apps/openbaar/Dockerfile

@@ -17,5 +17,9 @@ FROM nginx:1.27-alpine AS runtime
 COPY apps/openbaar/nginx.conf /etc/nginx/conf.d/default.conf
 COPY --from=build /src/dist/apps/openbaar/browser /usr/share/nginx/html
 # No runtime config: the openbaar register is anonymous (no OIDC authority to inject).
+# Make the reverse-proxy resolver engine-portable (Docker 127.0.0.11 vs podman aardvark); runs from
+# the nginx image's /docker-entrypoint.d before nginx starts.
+COPY apps/portal-nginx-resolver.sh /docker-entrypoint.d/40-resolver.sh
+RUN chmod +x /docker-entrypoint.d/40-resolver.sh
 
 EXPOSE 80

apps/portal-nginx-resolver.sh

@@ -0,0 +1,17 @@
+#!/bin/sh
+# Point nginx's reverse-proxy `resolver` at THIS container's real DNS server.
+#
+# The portal nginx configs use a variable proxy_pass, which needs a `resolver` so the BFF hostname is
+# resolved at request time (nginx can start before the BFF is up). The config hardcodes Docker's
+# embedded DNS (127.0.0.11) — correct on Docker/Docker Desktop, but rootless podman uses a
+# network-specific address (aardvark, e.g. 10.89.0.1), so proxied calls 502 there. Read the actual
+# nameserver from /etc/resolv.conf and substitute it, so the reverse proxy works on any engine.
+#
+# Runs from the nginx image's /docker-entrypoint.d/ before nginx starts. On Docker the nameserver IS
+# 127.0.0.11, so the substitution is a no-op. Guarded (no `set -e`) so it's safe whether the nginx
+# entrypoint executes or sources it.
+ns="$(awk '/^nameserver/{print $2; exit}' /etc/resolv.conf 2>/dev/null)"
+if [ -n "$ns" ] && [ "$ns" != "127.0.0.11" ]; then
+  sed -i "s/resolver 127\.0\.0\.11/resolver $ns/" /etc/nginx/conf.d/default.conf 2>/dev/null || true
+  echo "portal-nginx-resolver: set resolver to $ns"
+fi

apps/self-service/Dockerfile

@@ -19,5 +19,9 @@ COPY --from=build /src/dist/apps/self-service/browser /usr/share/nginx/html
 # Compose-time OIDC config: the browser (Playwright, on the compose network) reaches Keycloak by
 # service name, so the token issuer matches the BFF's authority (host-consistent, ADR-0010).
 RUN printf '{ "authority": "http://keycloak:8080/realms/digid" }\n' > /usr/share/nginx/html/config.json
+# Make the reverse-proxy resolver engine-portable (Docker 127.0.0.11 vs podman aardvark); runs from
+# the nginx image's /docker-entrypoint.d before nginx starts.
+COPY apps/portal-nginx-resolver.sh /docker-entrypoint.d/40-resolver.sh
+RUN chmod +x /docker-entrypoint.d/40-resolver.sh
 
 EXPOSE 80