Add shadow to popups in the native input

[YoussefKeyrouz]

Task/Issue URL: https://app.asana.com/1/137249556945/project/1204912272578138/task/1218154313912016?focus=true
Tech Design URL (if applicable):
API Proposals URL(s) (if applicable):

Description

This PR moves popup_menu_bg from the inner container to the ScrollView in all four views. g.

Steps to test this PR

• Open a Duck.ai chat with the native input enabled
• Open the model picker and confirm the menu has a drop shadow
• Open the effort picker and confirm the menu has a drop shadow
• Tap the attachment (+) button and confirm the menu has a drop shadow
• Open the tools menu (create image / web search) and confirm the menu has a drop shadow
• Repeat in dark mode

UI changes

Before	After

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[malmstein]

LGTM.