Rename user-visible instances of 'threads' to 'smiths'

[use-tusk[bot]]

We have updated all user-visible instances of the word 'threads' to 'smiths' in two files: src/components/layouts/site-footer.tsx and src/components/create-post-input.tsx. In the footer, 'Threads Terms' was changed to 'Smiths Terms'. In the create post input component, the placeholder text 'Start a thread...' was changed to 'Start a smith...'. This change ensures consistency with the new naming convention across the application.

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