feat: custom Logto image + auto-redirect to sign-in

- Add docker/logto.Dockerfile: builds custom Logto image with sign-in
  UI baked into /etc/logto/packages/experience/dist/
- Remove sign-in-ui init container, signinui volume, CUSTOM_UI_PATH
  (CUSTOM_UI_PATH is Logto Cloud only, not available in OSS)
- Remove sign-in build stage from SaaS Dockerfile (now in logto.Dockerfile)
- Remove docker/saas-entrypoint.sh (no longer needed)
- LoginPage auto-redirects to Logto OIDC on mount instead of showing
  "Sign in with Logto" button — seamless sign-in experience

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -58,16 +58,15 @@ services:
       - cameleer
 
   logto:
-    image: ghcr.io/logto-io/logto:latest
+    image: ${LOGTO_IMAGE:-gitea.siegeln.net/cameleer/cameleer-logto}:${VERSION:-latest}
+    build:
+      context: .
+      dockerfile: docker/logto.Dockerfile
     restart: unless-stopped
     depends_on:
       postgres:
         condition: service_healthy
-      sign-in-ui:
-        condition: service_completed_successfully
     entrypoint: ["sh", "-c", "npm run cli db seed -- --swe && npm start"]
-    volumes:
-      - signinui:/etc/logto/packages/experience/dist
     environment:
       DB_URL: postgres://${POSTGRES_USER:-cameleer}:${POSTGRES_PASSWORD:-cameleer_dev}@postgres:5432/logto
       ENDPOINT: ${PUBLIC_PROTOCOL:-https}://${PUBLIC_HOST:-localhost}
@@ -122,14 +121,6 @@ services:
     networks:
       - cameleer
 
-  sign-in-ui:
-    image: ${CAMELEER_IMAGE:-gitea.siegeln.net/cameleer/cameleer-saas}:${VERSION:-latest}
-    restart: "no"
-    user: root
-    entrypoint: ["sh", "-c", "cp -r /app/sign-in-dist/* /data/sign-in-ui/ && echo '[sign-in-ui] Copied custom UI to shared volume'"]
-    volumes:
-      - signinui:/data/sign-in-ui
-
   cameleer-saas:
     image: ${CAMELEER_IMAGE:-gitea.siegeln.net/cameleer/cameleer-saas}:${VERSION:-latest}
     restart: unless-stopped
@@ -250,4 +241,3 @@ volumes:
   certs:
   jardata:
   bootstrapdata:
-  signinui: