Add exclusion filters for steward submission review

[JoaquinBN]

Summary

Added two exclusion filters to the steward submission review page:

• Medium Blog Posts: Exclude all submissions with contribution type "Medium Blog Post"
• Submissions without URLs: Exclude submissions that lack both evidence URLs and URLs in the notes field

Filters use checkbox toggles with an "Apply" button for dynamic application alongside existing filters.

Testing

• Toggle "Medium Blog Posts" checkbox and click Apply to filter out blog posts
• Toggle "Submissions without URLs" checkbox to exclude text-only submissions
• Combine both filters to verify they work together
• Verify existing filters continue working normally