feat: close modals with browser back button on mobile (#257)

* feat: close modals with browser back button on mobile

Create reusable useModalHistory hook that pushes history state when a
modal opens and listens for popstate to close it. Apply to ReportModal,
ClearMissedConfirm, ExportModal, ImportConfirm, and all modals using
ConfirmModal/ShareDialog/Auth/ExportModal base components. Escape key
handling was already in place for desktop.

Closes #253

* fix: update tests for renamed button labels and missing useModalHistory mock

frontend/src/test/components/Auth.test.tsx

@@ -556,7 +556,7 @@ describe("UserProfile", () => {
 		);
 
 		await waitFor(() => {
-			const cancelBtn = screen.getByText(/common\.cancel/i);
+			const cancelBtn = screen.getByText(/common\.close/i);
 			fireEvent.click(cancelBtn);
 		});
 

frontend/src/test/components/ExportModal.test.tsx

@@ -70,12 +70,12 @@ describe("ExportModal", () => {
 
 	it("renders cancel button", () => {
 		render(<ExportModal {...defaultProps} />);
-		expect(screen.getByText(/exportImport\.cancelButton/i)).toBeInTheDocument();
+		expect(screen.getByText(/common\.close/i)).toBeInTheDocument();
 	});
 
 	it("calls onClose when cancel button is clicked", () => {
 		render(<ExportModal {...defaultProps} />);
-		fireEvent.click(screen.getByText(/exportImport\.cancelButton/i));
+		fireEvent.click(screen.getByText(/common\.close/i));
 		expect(defaultProps.onClose).toHaveBeenCalled();
 	});
 

frontend/src/test/components/ReportModal.test.tsx

@@ -30,7 +30,7 @@ describe("ReportModal", () => {
 		render(<ReportModal isOpen={true} onClose={onClose} medications={[createMedication()]} />);
 
 		expect(screen.getByText(/report\.title/i)).toBeInTheDocument();
-		fireEvent.click(screen.getByRole("button", { name: /common\.cancel/i }));
+		fireEvent.click(screen.getByRole("button", { name: /common\.close/i }));
 		expect(onClose).toHaveBeenCalledTimes(1);
 	});
 

frontend/src/test/components/ShareDialog.test.tsx

@@ -54,7 +54,8 @@ describe("ShareDialog", () => {
 
 	it("calls onClose when close button is clicked", () => {
 		render(<ShareDialog {...defaultProps} />);
-		fireEvent.click(screen.getByRole("button", { name: /common\.close/i }));
+		const closeButtons = screen.getAllByRole("button", { name: /common\.close/i });
+		fireEvent.click(closeButtons[closeButtons.length - 1]);
 		expect(defaultProps.onClose).toHaveBeenCalled();
 	});