[Core] fix failed to filter invalid images in special cases

[DarkRRb]

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[Copilot]

Pull Request Overview

This PR addresses the filtering issue for invalid images by updating the URI validation to only consider absolute URIs.

• Updated image URL validation logic in OldAndInvalidImageFilterRule.
• Ensures that only images with absolute URLs pass the well-formed check.

Comments suppressed due to low confidence (1)

Lagrange.Core/Message/Filter/Rule/OldAndInvalidImageFilterRule.cs:17

• The change to only accept absolute URIs enhances the filtering logic; however, please verify that no valid relative URIs are expected elsewhere in the application.

if (!Uri.IsWellFormedUriString(image.ImageUrl, UriKind.Absolute)) return ImageType.Invalid;