Better Clarity and Stability in Mind Maps

🛠 Fixes

• Fixed: Freezing in the desktop app caused by repeated Yjs initialization after disconnections

✨ New Features

• Show "Element deleted" only for branches that previously had content — avoids confusing messages when removing empty elements

🔄 Improvements

• Removed placeholder from center editable text — cleaner look
• Reduced width of first-level branches with text for more compact layout
  • Before → After

And other improvements