fix(ai-backend): Configure Ollama service with host address mode

The `ollama` service in the `ai-backend` Nomad job has been updated to use `address_mode = "host"`. This ensures the service is registered with the host's IP address in Consul, allowing external proxies like Traefik to correctly route traffic. This change resolves potential connectivity issues by making the service directly accessible via the host network.

stacks/ai/ai-backend.nomad

@@ -50,6 +50,7 @@ job "ai-backend" {
         name = "ollama"
         port = "api"
         tags = ["traefik.enable=true"]
+        address_mode = "host"
         check {
           type     = "http"
           path     = "/"