refactor: use foreignId methods in the CreateMediaTable migration

[artengin]

Refs: #68

[Copilot]

Pull Request Overview

This PR refactors the CreateMediaTable migration to use Laravel's fluent foreignId methods instead of separate column definition and foreign key constraint declaration. This modernizes the migration code to follow Laravel's current best practices for defining foreign key relationships.

• Replaced separate integer('owner_id') and foreign('owner_id') declarations with a single fluent foreignId('owner_id') chain
• Moved the foreignId('preview_id') definition from column declaration to the foreign key constraint section and updated to use cascadeOnDelete()

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