feat: extend undo/redo for interface and cable operations

[ggfevans]

Parent Epic

Part of #71 (Network Interface Visualization and Connectivity)

Summary

Extend the undo/redo system to support interface and cable operations.

Current Undo Support

• Device add/remove/move
• Rack property changes
• Layout settings changes

New Operations to Support

• Add interface to device type
• Remove interface from device type
• Edit interface properties
• Create cable
• Delete cable
• Edit cable properties
• Bulk interface add

Technical Approach

Use existing history store pattern:

• Snapshot relevant state before operation
• Push to history stack
• Restore on undo

Considerations

• Device type changes affect all placements of that type
• Cable deletion orphans connection data
• Bulk operations should be single undo step

Acceptance Criteria

• All interface operations undoable
• All cable operations undoable
• Bulk operations undo as single step
• Redo works correctly
• History limit respected (existing: 50 steps)

Dependencies

• feat: expand InterfaceTemplate type and Zod schema #247 (InterfaceTemplate schema)
• feat: cable data model and schema #261 (Cable data model)

References

• History store: src/lib/stores/history.svelte.ts