[WIP] Update based on feedback for chatbot improvement PR

[Copilot]

• Add configuration constants for mount limits (max files, max folders, max depth)
• Implement pre-mount validation to estimate directory size and depth
• Add early termination logic during mounting if limits are exceeded
• Update endpoint to return appropriate error messages when limits are hit
• Test the implementation with edge cases
• Address code review feedback (path normalization, consistent depth checks, partial count handling)
• Clarify depth limit semantics and improve constant definitions
• Run security checks (no issues found)

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