Fix staging containers failing on Windows Docker builds

Strip CRLF from entrypoint scripts in backend/frontend images, use Docker
DNS in staging nginx config, and wait for healthy app services before nginx.

Co-authored-by: Cursor <cursoragent@cursor.com>

infrastructure/nginx/http-only.conf

@@ -1,15 +1,10 @@
 # HTTP only — local dev and IP-based staging (no TLS).
 # Use with: docker compose and map host port e.g. 8080:80 or 8088:80
+#
+# Dynamic proxy_pass via Docker DNS (127.0.0.11) so nginx starts even if
+# backend/frontend containers are not up yet (static upstream blocks fail at boot).
 
-upstream dyolink_backend {
-    server backend:3000;
-    keepalive 32;
-}
-
-upstream dyolink_frontend {
-    server frontend:3000;
-    keepalive 32;
-}
+resolver 127.0.0.11 valid=10s ipv6=off;
 
 server {
     listen 80;
@@ -19,7 +14,8 @@ server {
     client_max_body_size 50M;
 
     location / {
-        proxy_pass http://dyolink_frontend;
+        set $frontend_upstream http://frontend:3000;
+        proxy_pass $frontend_upstream;
         proxy_http_version 1.1;
         proxy_set_header Upgrade $http_upgrade;
         proxy_set_header Connection 'upgrade';
@@ -33,7 +29,8 @@ server {
     }
 
     location /api {
-        proxy_pass http://dyolink_backend;
+        set $backend_upstream http://backend:3000;
+        proxy_pass $backend_upstream;
         proxy_http_version 1.1;
         proxy_set_header Upgrade $http_upgrade;
         proxy_set_header Connection 'upgrade';