chore: Shell UX papercuts

[jsantell]

• Clean up extra paddings around components. Broadly, removed styling for content elements, and handle it in positional elements
• Some reusable components: x-button, x-flex, h-box, v-box
  • Apply throughout
  • Maybe we want to use v1/v2 components here. I didn't think too hard about these

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Summary by cubic

Improved the shell UI by adding reusable Button and Flex components, simplifying layout code, and updating login and header actions to use the new components.

• UI Improvements
  • Replaced custom button styles with a new component across the shell.
  • Added , , and components for easier layout and alignment.
  • Cleaned up and removed redundant styles from several components.
  • Updated login and header actions to use the new components for consistency.