Set up image placeholders

[VictorKabata]

Description

• Set up image placeholder for movies and cast

Issue

N/A

Screenshots / GIFs

N/A

Checklist

• [x] I have tested the changes on both Android, iOS and Desktop platforms.
• [ ] I have written unit tests for the new code (if applicable).
• [x] I have updated the project's documentation (if necessary).
• [x] I have checked for any potential code duplications and removed them.
• [x] I have run the Kotlin/Compose Multiplatform Gradle tasks and verified that they were completed successfully.
• [x] I have considered the impact of these changes on the existing codebase.

Additional Notes

N/A