fix generated media history URLs

[zhonggang666]

What this PR does / why we need it?

Fixes generated media history replay so stored image metadata dictionaries are converted back into actual image URLs.

Closes #6371.

Summary of your change

• Adds a small helper to normalize historical image_list entries.
• Supports both existing string entries and current { file_id, url } metadata dictionaries.
• Replays the actual URL instead of the string representation of the whole Python dict.

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.

Validation:

• python -m py_compile apps/application/flow/step_node/image_generate_step_node/impl/base_image_generate_node.py apps/application/flow/step_node/text_to_video_step_node/impl/base_text_to_video_node.py apps/application/flow/step_node/image_to_video_step_node/impl/base_image_to_video_node.py
• git diff --check