feat: cable data model and schema

[ggfevans]

Parent Epic

Part of #71 (Network Interface Visualization and Connectivity)

Summary

Design and implement the data model for cable connections between device interfaces.

Data Model

interface Cable {
  id: string;                    // UUID

  // A-side termination
  a_device_id: string;           // Placed device UUID
  a_interface: string;           // Interface name

  // B-side termination
  b_device_id: string;
  b_interface: string;

  // Cable properties
  type?: CableType;
  color?: string;                // 6-digit hex
  label?: string;
  length?: number;
  length_unit?: 'm' | 'cm' | 'ft' | 'in';
  status?: 'connected' | 'planned' | 'decommissioning';
}

type CableType =
  | 'cat5e' | 'cat6' | 'cat6a' | 'cat7' | 'cat8'
  | 'dac-passive' | 'dac-active'
  | 'mmf-om3' | 'mmf-om4' | 'smf-os2'
  | 'aoc'
  | 'power'
  | 'serial';

Acceptance Criteria

• Define Cable interface in types/index.ts
• Create CableSchema in schemas/index.ts
• Add cables array to Layout type
• Update LayoutSchema
• Ensure YAML serialization works
• Create cable store (cables.svelte.ts)
• Add cable CRUD operations

Storage Location

interface Layout {
  // ... existing fields
  cables?: Cable[];  // New field
}

Validation Rules

• a_device_id and b_device_id must exist in rack.devices
• a_interface must exist on a_device's device type
• b_interface must exist on b_device's device type
• No duplicate cables (same A and B endpoints)

References

• NetBox cable model: docs/research/netbox-interface-cable-schema.md
• Spike research: spike: Network interface visualization research #237