Add CSRF token hidden input fields to:
- Submission form (submission/form.html)
- Login form (auth/login.html)
Also fix broken link in login page that referenced submission.form
without required product_slug parameter. Changed to link to index page.
Bug found during manual testing when submitting feedback resulted in
"Bad Request - The CSRF token is missing" error.
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Co-Authored-By: Claude <noreply@anthropic.com>