feat: integrate Pi backend and Pi Web

pi-web/app/api/sessions/[id]/state/route.ts

@@ -0,0 +1,23 @@
+import { NextResponse } from "next/server";
+import { getRpcSession } from "@/lib/rpc-manager";
+import { resolveSessionPath } from "@/lib/session-reader";
+
+export async function GET(
+  _req: Request,
+  { params }: { params: Promise<{ id: string }> },
+) {
+  const { id } = await params;
+  try {
+    if (!await resolveSessionPath(id)) {
+      return NextResponse.json({ error: "Session not found" }, { status: 404 });
+    }
+
+    const rpc = getRpcSession(id);
+    if (!rpc?.isAlive()) return NextResponse.json({ running: false });
+
+    const state = await rpc.send({ type: "get_state" });
+    return NextResponse.json({ running: true, state });
+  } catch (error) {
+    return NextResponse.json({ error: String(error) }, { status: 500 });
+  }
+}