Add Lock / Unlock mode for selected nodes or subtrees

[hsayed21]

Problem

When working on large collaborative mind maps, some nodes or branches may already be finalized.

However, users can still accidentally:

• Move nodes.
• Rename nodes.
• Delete nodes.
• Change colors or styling.
• Modify an existing branch while editing nearby nodes.

This is especially risky in collaborative maps, where multiple users may be editing at the same time.

Proposed Solution

Add a Lock / Unlock action in the toolbar.

Users should be able to:

• Select one node and lock it.
• Select multiple nodes and lock them.
• Select a parent node and lock the entire subtree.
• Unlock nodes later when editing is needed.

Suggested UX

Add a toolbar button:

🔒 Lock / 🔓 Unlock

When a node is locked:

• It cannot be moved.
• It cannot be renamed.
• It cannot be deleted.
• Its style/colors cannot be changed.
• Its parent-child relationship cannot be changed.

Optional behavior:

• Locked nodes could still allow child nodes to be added, depending on project preference.
• Or fully lock the subtree including adding/removing children.

Visual Indicator

Locked nodes should have a small lock icon or visual state, for example:

🔒 John

or a small lock badge in the node corner.

Benefits

• Prevents accidental changes.
• Makes collaboration safer.
• Protects finalized branches.
• Improves confidence when sharing edit links with many people.
• Very useful for large family trees, organization charts, and project maps.