fix: fallback missing realm card image

[SameDesu123]

PR Checklist

• Required Checks
  • Have you added type definitions?
  • Have you tested your changes?
  • Have you checked that it won't break any existing features?
• If your PR uses models¹, check the following:
  • Have you checked if it works normally in all models?
  • Have you checked if it works normally in all web, local, and node-hosted versions? If it doesn't, have you blocked it in those versions?
• If your PR is highly AI generated², check the following:
  • Have you understood what the code does?
  • Have you cleaned up any unnecessary or redundant code?
  • Is it not a huge change?

Summary

Adds a fallback image for character card exports when the character has no readable avatar image.

Related Issues

None

Changes

• Added a character card export image resolver that first tries the character image.
• Falls back to /none.webp when the character image is missing, empty, or unreadable.
• Keeps the fallback limited to export/upload output without mutating the character or database image field.

Impact

Realm uploads and character card exports no longer fail solely because a bot card has no profile image. Existing characters with valid images continue to export with their original image.

Additional Notes

Validated with pnpm check.
Test it manually in dev server.

Footnotes

1. Modifies the behavior of prompting, requesting, or handling responses from AI models. ↩

2. Over 80% of the code is AI generated. ↩

[cubicj]

Verified the export path. This reuses the existing /none.webp placeholder for missing card images without mutating the character data.

Check, tests, and build pass locally.

Approving — thanks for the contribution!