feat(developer): add hybrid iframe integration for developer tools

Replace placeholder pages with ToolEmbed component that embeds
LangGraph, LangFlow, and Langfuse in iframes when configured, or
shows "Not Configured" placeholders when URLs are empty. Add
ServiceUrlsContext for passing service URLs through Dioxus context.

Add docker-compose services for local development: LangFlow,
LangGraph (trial), Langfuse with full dependency stack (Postgres,
ClickHouse, Redis, MinIO).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/pages/developer/agents.rs

@@ -1,27 +1,27 @@
 use dioxus::prelude::*;
 
+use crate::components::ToolEmbed;
 use crate::i18n::{t, Locale};
+use crate::models::ServiceUrlsContext;
 
-/// Agents page placeholder for the LangGraph agent builder.
+/// Agents page embedding the LangGraph agent builder.
 ///
-/// Shows a "Coming Soon" card with a disabled launch button.
-/// Will eventually integrate with the LangGraph framework.
+/// When `langgraph_url` is configured, embeds the service in an iframe
+/// with a pop-out button. Otherwise shows a "Not Configured" placeholder.
 #[component]
 pub fn AgentsPage() -> Element {
     let locale = use_context::<Signal<Locale>>();
+    let svc = use_context::<Signal<ServiceUrlsContext>>();
     let l = *locale.read();
+    let url = svc.read().langgraph_url.clone();
 
     rsx! {
-        section { class: "placeholder-page",
-            div { class: "placeholder-card",
-                div { class: "placeholder-icon", "A" }
-                h2 { "{t(l, \"developer.agents_title\")}" }
-                p { class: "placeholder-desc",
-                    "{t(l, \"developer.agents_desc\")}"
-                }
-                button { class: "btn-primary", disabled: true, "{t(l, \"developer.launch_agents\")}" }
-                span { class: "placeholder-badge", "{t(l, \"common.coming_soon\")}" }
-            }
+        ToolEmbed {
+            url,
+            title: t(l, "developer.agents_title"),
+            description: t(l, "developer.agents_desc"),
+            icon: "A",
+            launch_label: t(l, "developer.launch_agents"),
         }
     }
 }