Fix agent IP detection to use real client IP from proxy headers

The agent's last_seen IP was showing the Docker container IP (10.244.x.x)
because conn.remote_ip returns the proxy/load balancer IP.

Changes:
- Added get_client_ip/1 helper that checks X-Forwarded-For first
- Falls back to X-Real-IP if X-Forwarded-For not present
- Falls back to conn.remote_ip as last resort
- Applied to both AgentAuth plug and AgentController heartbeat endpoint

Now correctly shows the actual external IP of the remote agent.

lib/towerops_web/controllers/api/agent_controller.ex

@@ -91,7 +91,7 @@ defmodule ToweropsWeb.Api.AgentController do
   """
   def heartbeat(conn, params) do
     agent_token = conn.assigns.current_agent_token
-    ip = to_string(:inet_parse.ntoa(conn.remote_ip))
+    ip = get_client_ip(conn)
 
     # Parse metadata based on content type
     metadata =
@@ -320,4 +320,29 @@ defmodule ToweropsWeb.Api.AgentController do
   defp convert_metadata_to_proto(metadata) when is_map(metadata) do
     Map.new(metadata, fn {k, v} -> {to_string(k), to_string(v)} end)
   end
+
+  # Get the real client IP, checking forwarded headers first
+  defp get_client_ip(conn) do
+    # Check X-Forwarded-For header first (set by load balancers/proxies)
+    case get_req_header(conn, "x-forwarded-for") do
+      [forwarded | _] ->
+        # X-Forwarded-For can have multiple IPs (client, proxy1, proxy2...)
+        # Take the first one (original client)
+        forwarded
+        |> String.split(",")
+        |> List.first()
+        |> String.trim()
+
+      [] ->
+        # Fall back to X-Real-IP
+        case get_req_header(conn, "x-real-ip") do
+          [real_ip | _] ->
+            String.trim(real_ip)
+
+          [] ->
+            # Fall back to conn.remote_ip
+            to_string(:inet_parse.ntoa(conn.remote_ip))
+        end
+    end
+  end
 end

lib/towerops_web/plugs/agent_auth.ex

@@ -42,7 +42,7 @@ defmodule ToweropsWeb.Plugs.AgentAuth do
   end
 
   defp update_heartbeat(conn, agent_token) do
-    ip = to_string(:inet_parse.ntoa(conn.remote_ip))
+    ip = get_client_ip(conn)
 
     # In test environment, update synchronously to avoid DB ownership issues
     # In production, update asynchronously for better performance
@@ -55,6 +55,31 @@ defmodule ToweropsWeb.Plugs.AgentAuth do
     conn
   end
 
+  # Get the real client IP, checking forwarded headers first
+  defp get_client_ip(conn) do
+    # Check X-Forwarded-For header first (set by load balancers/proxies)
+    case get_req_header(conn, "x-forwarded-for") do
+      [forwarded | _] ->
+        # X-Forwarded-For can have multiple IPs (client, proxy1, proxy2...)
+        # Take the first one (original client)
+        forwarded
+        |> String.split(",")
+        |> List.first()
+        |> String.trim()
+
+      [] ->
+        # Fall back to X-Real-IP
+        case get_req_header(conn, "x-real-ip") do
+          [real_ip | _] ->
+            String.trim(real_ip)
+
+          [] ->
+            # Fall back to conn.remote_ip
+            to_string(:inet_parse.ntoa(conn.remote_ip))
+        end
+    end
+  end
+
   defp update_heartbeat_async(agent_token_id, ip) do
     parent = self()