fix: redirect to home after creating first user

[igboyes]

Summary

• After creating the first user, the app now invalidates the root query cache and navigates to / using TanStack Router instead of reloading the page via window.location.reload()
• The onSuccess handler was moved from the mutation definition in useCreateFirstUser to the call site in FirstUser.tsx so that navigation concerns stay in the component
• Clarifies conventional commit type guidelines in AGENTS.md, noting that only feat and fix trigger semantic-release and describing when to use each type

Test plan

• Updated test uses renderWithRouter and asserts router.state.location.pathname === "/" after form submission
• Manually verify that submitting the first-user form redirects to the home page without a full page reload

[gemini-code-assist]

Code Review

This pull request updates the Git commit message guidelines in AGENTS.md and refactors the first-user creation process. The useCreateFirstUser hook's automatic page reload was replaced with programmatic navigation and query invalidation within the FirstUser component. Additionally, the associated test was updated to verify the redirect and reflect changes to the API endpoint method. I have no feedback to provide.