fix(FN-700): remove duplicate mobile overflow menu buttons and clean up dead code

- Remove duplicate Terminal and Schedules buttons from mobile overflow menu in Header
- Remove unused CSS styles for mobile overflow menu items
- Clean up dead/duplicate route handler code in routes.ts
- Simplify TaskCard script button rendering logic
- Add tests for mobile Scripts button visibility in Header

packages/dashboard/app/components/Header.test.tsx

@@ -365,6 +365,20 @@ describe("Header", () => {
       fireEvent.click(screen.getByTestId("overflow-terminal-btn"));
       expect(onToggleTerminal).toHaveBeenCalled();
     });
+
+    it("shows scripts in overflow menu on mobile", () => {
+      renderHeader({ onOpenScripts: noop }, true);
+      fireEvent.click(screen.getByTitle("More header actions"));
+      expect(screen.getByTestId("overflow-scripts-btn")).toBeDefined();
+    });
+
+    it("calls onOpenScripts from mobile overflow menu", () => {
+      const onOpenScripts = vi.fn();
+      renderHeader({ onOpenScripts }, true);
+      fireEvent.click(screen.getByTitle("More header actions"));
+      fireEvent.click(screen.getByTestId("overflow-scripts-btn"));
+      expect(onOpenScripts).toHaveBeenCalled();
+    });
   });
 
   describe("search functionality", () => {