feat: add newsfeed widget (#384)

[MatthewTighe]

This PR adds a newsfeed widget using Jetpack Glance for #384. It:

• establishes a separate "current feed and tag" for the widget
• allows customization of the display feed and tag through a settings activity
• allows refreshing the widget through a "refresh button"

There are a couple areas that could potentially use more polish, but I wanted to get this up to at least start a conversation as to whether it is worth waiting for them.

Areas of potential improvement:

1. the widget preview never renders, just loads forever
2. lack of tests - Glance is allegedly unit testable, but because this access LocalContext, it would need to provided by something like Robolectric, which I did not think was worth importing for that alone. there's otherwise very little logic here, but happy to eventually add tests for the Repository etc if preferred
3. I can't get the "Refreshing" text to actually display for some reason - though it does if I make that the only content. I'll probably keep messing with this at some point
4. widget isn't resizable

LMK your thoughts on whether any of these are worth baking longer - happy to keep trucking on this but it's obviously been slow going. Assume we will just squash these commits as well?

Screen_recording_20260106_222913.webm