feat(frontend): add intake journal and shared note flows (#648)

* feat(backend): add intake journal APIs and share note support

* feat(frontend): add intake journal and shared note flows

frontend/src/test/hooks/useModalHistory.test.ts

@@ -0,0 +1,47 @@
+import { act, renderHook } from "@testing-library/react";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { useModalHistory } from "../../hooks/useModalHistory";
+
+describe("useModalHistory", () => {
+	beforeEach(() => {
+		vi.spyOn(window.history, "pushState").mockImplementation(() => {});
+	});
+
+	afterEach(() => {
+		vi.restoreAllMocks();
+	});
+
+	it("pushes a modal history entry and closes the modal on browser back", () => {
+		const onClose = vi.fn();
+		const { rerender } = renderHook(({ isOpen }) => useModalHistory(isOpen, "journal-editor", onClose), {
+			initialProps: { isOpen: false },
+		});
+
+		rerender({ isOpen: true });
+
+		expect(window.history.pushState).toHaveBeenCalledWith({ modal: "journal-editor" }, "");
+
+		act(() => {
+			window.dispatchEvent(new PopStateEvent("popstate"));
+		});
+
+		expect(onClose).toHaveBeenCalledTimes(1);
+	});
+
+	it("stops parent popstate handlers when a nested modal consumes browser back", () => {
+		const onClose = vi.fn();
+		const parentClose = vi.fn();
+		window.addEventListener("popstate", parentClose);
+
+		renderHook(() => useModalHistory(true, "nested-confirm", onClose));
+
+		act(() => {
+			window.dispatchEvent(new PopStateEvent("popstate"));
+		});
+
+		expect(onClose).toHaveBeenCalledTimes(1);
+		expect(parentClose).not.toHaveBeenCalled();
+
+		window.removeEventListener("popstate", parentClose);
+	});
+});