fix(tiptap): generate unique contentKeys when pasting blocks

[ronstarling9]

Problem

• When copying and pasting blocks in tiptap editor, duplicate contentKeys are created
• This causes issues with block identification and content management

Solution

• Generate new unique contentKeys when pasting blocks
• Ensures each pasted block has a distinct identifier

Testing

• Build successful
• Tested copy/paste functionality with multiple blocks

Fixes #20568

[github-actions]

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