Previously, signing up gave immediate access to the app. Now,
unconfirmed users are redirected to a verification page where they can
resend the confirmation email.
- After signup, the user is routed to `/auth/verify-email` instead of
the dashboard
- After login, unconfirmed users are redirected to the verification page
- The dashboard route guard catches unconfirmed users and redirects them
- `active_for_authentication?` is removed from the sessions controller
so unconfirmed users can authenticate — the frontend gates access
instead
- If the user visits the verification page after already confirming,
they're automatically redirected to the dashboard
- No session is issued until the user is verified
<details><summary>Demo</summary>
<p>
#### Fresh Signup
https://github.com/user-attachments/assets/abb735e5-7c8e-44a2-801c-96d9e4823e51
#### Google Fresh Signup
https://github.com/user-attachments/assets/ab9e389a-a604-4a9d-b492-219e6d94ee3f
#### Create new account from Dashboard
https://github.com/user-attachments/assets/c456690d-1946-4e0b-834b-ad8efcea8369
</p>
</details>
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Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
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