Fix: Copy session name should not be whitespace only

[luisa12ll]

Description

Fixes #12679

Problem:
Currently, when copying a session and deleting the identical name, the "Name for copied session" field validation allows whitespace-only names, which violates the system rules.

Solution:

• Added validation to prevent empty or whitespace-only session names
• Copy button is disabled for invalid names
• Error message is displayed for invalid inputs
• Form submission is blocked for invalid names

Changes Made

Functional Changes

• Added isWhitespaceOnly() method to detect whitespace strings
• Enhanced validateForm() to include whitespace validation
• Added form state management with isFormValid property
• Connected validation to UI events

Test Changes

• Added test for disabled copy button with whitespace names
• Added test for error message display
• Fixed existing tests to work with new validation
• All 1457 tests pass successfully

Testing

• ✅ Manual testing with various input scenarios
• ✅ All unit tests pass (1457/1457)
• ✅ Integration with existing validation rules
• ✅ No regressions introduced

Screenshots

(If applicable, add screenshots of the error message and disabled button)

[github-actions]

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