fix: use host Docker socket with isolated E2E network

The per-job DinD approach failed because Forgejo Runner's service container
DNS resolution does not work when the runner itself uses DinD
(container.docker_host: tcp://dind:2375). The job container could not resolve
the 'dind' service hostname, causing docker compose to fail immediately.

New approach:

- Runner now uses container.docker_host: 'automount' which mounts the host
  Docker socket into job containers. The runner runs as root (user: 0:0)
  to access /var/run/docker.sock.

- E2E job no longer uses a 'dind' service. docker compose runs directly
  against the host Docker daemon inside the job container.

- docker-compose.e2e.yml gets a custom 'e2e' bridge network. All E2E
  containers (postgres, backend, frontend, playwright) attach only to this
  network, isolating them from other host containers (Nextcloud, Jellyfin,
  etc.). They can still reach the internet for vehicle lookup and npm.

Tradeoff: job containers can see other containers via docker ps, but they
are on an isolated network. For a single-user home server, this is the
simplest reliable configuration.

.forgejo/workflows/ci.yml

@@ -58,14 +58,7 @@ jobs:
   e2e:
     name: E2E browser tests
     runs-on: ubuntu-latest
-    services:
-      dind:
-        image: docker:28-dind
-        options: --privileged
-        env:
-          DOCKER_TLS_CERTDIR: ""
     env:
-      DOCKER_HOST: tcp://dind:2375
       POSTGRES_DB: bilhej
       POSTGRES_USER: bilhej
       POSTGRES_PASSWORD: test_pw_ci_123

docker-compose.e2e.yml

@@ -1,3 +1,7 @@
+networks:
+  e2e:
+    driver: bridge
+
 services:
   postgres:
     image: postgres:16
@@ -6,6 +10,8 @@ services:
       POSTGRES_DB: ${POSTGRES_DB}
       POSTGRES_USER: ${POSTGRES_USER}
       POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
+    networks:
+      - e2e
     healthcheck:
       test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER} -d ${POSTGRES_DB}"]
       interval: 5s
@@ -26,6 +32,8 @@ services:
       STRIPE_SECRET_KEY: ${STRIPE_SECRET_KEY}
       STRIPE_WEBHOOK_SECRET: ${STRIPE_WEBHOOK_SECRET}
       STRIPE_PRICE_ID: ${STRIPE_PRICE_ID}
+    networks:
+      - e2e
     depends_on:
       postgres:
         condition: service_healthy
@@ -35,6 +43,8 @@ services:
       dockerfile: docker/frontend.e2e.Dockerfile
       context: .
     container_name: bilhej-frontend-e2e
+    networks:
+      - e2e
     depends_on:
       - backend
 
@@ -46,6 +56,8 @@ services:
     ipc: host
     environment:
       PLAYWRIGHT_BASE_URL: http://frontend
+    networks:
+      - e2e
     depends_on:
       - frontend
     command: >-