refactor(nomad): Centralize DNS configuration for AI frontends

Moves DNS server and search domain configuration from task `config` blocks to the job/group `network` blocks for `ai-frontend` (OpenWebUI) and `lobechat`.

This refactoring centralizes DNS settings for all tasks within a Nomad job or group, ensuring consistent DNS resolution and aligning with recommended Nomad configuration patterns.

stacks/ai/ai-frontend.nomad

@@ -17,15 +17,22 @@ job "ai-frontend" {
         static = 8080
         to     = 8080
       }
+      
+      # ✅ DNS Moved Here
+      dns {
+        servers  = ["192.168.1.133"]
+        searches = ["service.consul"]
+      }
     }
 
     service {
       name = "openwebui"
       port = "http"
       tags = ["traefik.enable=true"]
+      
       check {
         type     = "http"
-        path     = "/health" # OpenWebUI actually HAS this endpoint
+        path     = "/health"
         interval = "20s"
         timeout  = "2s"
       }
@@ -44,10 +51,7 @@ job "ai-frontend" {
         volumes = [
           "/mnt/local-ssd/nomad/stacks/ai/ai-frontend/openwebui:/app/backend/data"
         ]
-        
+        # Removed invalid dns_servers/dns_search from here
-        # DNS Fix
-        dns_servers = ["192.168.1.133"]
-        dns_search  = ["service.consul"]
       }
 
       resources {
@@ -71,6 +75,12 @@ job "ai-frontend" {
         static = 3210
         to     = 3210
       }
+
+      # ✅ DNS Moved Here
+      dns {
+        servers  = ["192.168.1.133"]
+        searches = ["service.consul"]
+      }
     }
 
     service {
@@ -78,8 +88,6 @@ job "ai-frontend" {
       port = "http"
       tags = ["traefik.enable=true"]
 
-      # --- THE FIX ---
-      # Changed from /api/health to / (Root)
       check {
         type     = "http"
         path     = "/"
@@ -99,10 +107,7 @@ job "ai-frontend" {
       config {
         image = "docker.io/lobehub/lobe-chat:v1.143.0"
         ports = ["http"]
-        
+        # Removed invalid dns_servers/dns_search from here
-        # DNS Fix
-        dns_servers = ["192.168.1.133"]
-        dns_search  = ["service.consul"]
       }
 
       resources {