fix: stabilize dashboard modal and image click behavior (#267)

* feat: make medication names clickable in Dashboard dose schedule

Add click handlers to med-name-stack divs in all three dose schedule
sections (past, current/overdue, future) on DashboardPage, opening the
MedDetail modal on click.

Add early-return guards to all four modal openers in AppContext
(openMedDetail, openImageLightbox, openScheduleLightbox, openUserFilter)
to prevent duplicate pushState entries on double-click, which caused
unexpected navigation to the Medications page.

Closes #266

* fix: stabilize dashboard modal and image click handling

* fix: close medication detail on first backdrop click

frontend/src/test/components/Lightbox.test.tsx

@@ -48,9 +48,10 @@ describe("Lightbox", () => {
 
 	it("calls onClose when Escape key is pressed", () => {
 		const onClose = vi.fn();
-		render(<Lightbox {...defaultProps} onClose={onClose} />);
+		const { container } = render(<Lightbox {...defaultProps} onClose={onClose} />);
 
-		fireEvent.keyDown(document, { key: "Escape" });
+		const overlay = container.querySelector(".lightbox-overlay");
+		fireEvent.keyDown(overlay!, { key: "Escape" });
 
 		expect(onClose).toHaveBeenCalled();
 	});