feat: Support batch import for Docker images

[CN-Scars]

What this PR does / why we need it?

Refs #11634

Summary of your change

Backend (Agent):

• Modified ImageLoad DTO to accept an array of paths (Paths []string) instead of a single path
• Updated the image service to iterate through multiple files and create subtasks for each import operation

Frontend:

• Added multiple prop support to the FileList component for multi-file selection
• Enabled multi-select mode in the image load dialog by passing multiple: true

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.

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