Refactored Back to Results button in Domain/Vuln Details (CRASM-761)

[hawkishpolicy]

• Refactored Back to Results button in Domain/Vuln Details view.
• Buttons were not uniform in structure, function, or styling.

  🗣 Description

• Converted link in Vuln Details to a button with a back arrow icon.
• Refined existing back button in Domain Details.
• Removed "Vulnerability Details" from the top of the Vuln Details page.
• Wrapped the Vuln Details page in a box with padding to match the Domain Details page.
• Ensured both buttons link back to their respective tables.

💭 Motivation and context

• Closes [CRASM-761] (https://maestro.dhs.gov/jira/browse/CRASM-761)

🧪 Testing

• Tested Locally.

📷 Screenshots (if appropriate)

✅ Pre-approval checklist

• [x] This PR has an informative and human-readable title.
• [x] Changes are limited to a single goal - eschew scope creep!
• [x] All future TODOs are captured in issues, which are referenced in code comments.
• [x] All relevant type-of-change labels have been added.
• [x] I have read the CONTRIBUTING document.
• [x] These code changes follow cisagov code standards.
• [ ] All relevant repo and/or project documentation has been updated to reflect the changes in this PR.
• [ ] Tests have been added and/or modified to cover the changes in this PR.
• [x] All new and existing tests pass.

✅ Pre-merge checklist

• [ ] Revert dependencies to default branches.
• [ ] Finalize version.

✅ Post-merge checklist

• [ ] Create a release.