fix: explicit docker network for rock solid DNS resolution

Completely removes the Nginx resolver hack. By assigning all services
to a dedicated custom bridge network ('autopilot-net') and relying on
docker-compose 'depends_on', Docker's internal DNS is guaranteed to
resolve the 'autopilot-master' hostname cleanly at Nginx startup without
SERVFAILs.

docker-compose.yml

@@ -18,6 +18,8 @@ services:
       interval: 10s
       timeout: 5s
       retries: 5
+    networks:
+      - autopilot-net
 
   # ─── AutoPilot Master (Cloud Coordinator Backend) ─────────────────────────
   master:
@@ -42,6 +44,8 @@ services:
       postgres:
         condition: service_healthy
     restart: unless-stopped
+    networks:
+      - autopilot-net
 
   # ─── AutoPilot UI (React Frontend via Nginx) ───────────────────────────────
   ui:
@@ -56,6 +60,8 @@ services:
     depends_on:
       - master
     restart: unless-stopped
+    networks:
+      - autopilot-net
 
   # ─── AutoPilot Worker (Execution Engine) ──────────────────────────────────
   # NOTE: The worker needs access to a real browser (Chrome/Firefox).
@@ -74,6 +80,13 @@ services:
   #   depends_on:
   #     - master
   #   restart: unless-stopped
+  #   networks:
+  #     - autopilot-net
+
+networks:
+  autopilot-net:
+    driver: bridge
 
 volumes:
   postgres_data:
+

ui/nginx.conf

@@ -5,10 +5,6 @@ server {
     # Allow large request bodies (screenshots are base64 encoded)
     client_max_body_size 50M;
 
-    # Use Docker's internal DNS resolver (disable IPv6 to prevent SERVFAIL)
-    resolver 127.0.0.11 ipv6=off valid=30s;
-    set $backend http://master:9090;
-
     # Serve static files from the React build
     location / {
         root   /usr/share/nginx/html;
@@ -18,7 +14,7 @@ server {
 
     # Reverse proxy API requests to the Master backend container
     location /api/ {
-        proxy_pass $backend;
+        proxy_pass http://autopilot-master:9090;
 
         # Standard proxy headers
         proxy_set_header Host $host;