[nav] Create style sheet and directory for every (tabs) screen

[akshaynthakur]

What's new in this PR

• Reorganize routing to remove nested screens and give each screen it's own directory with a styles sheet and layout file within the directory

Relevant Links

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Notion Sprint Task

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Online sources

How to hide screens from bottom tabs: https://docs.expo.dev/router/advanced/tabs/

Related PRs

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How to review

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Next steps

• Update routing in a similar fashion for all auth screens

Tests Performed, Edge Cases

• Checked navigating to all screens to make sure all routing works properly

Screenshots

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CC: @akshaynthakur