feat: port details panel in EditPanel

[ggfevans]

Parent Epic

Part of #71 (Network Interface Visualization and Connectivity)

Summary

When a port is clicked, show its details in the EditPanel sidebar.

Acceptance Criteria

• Add "Port Details" section to EditPanel when port is selected
• Display port name, type, label
• Display PoE information if applicable
• Display management-only flag
• Show connection info (future: which device/port connected to)
• Allow editing port properties (name, label)
• "Deselect port" returns to device details

UI Design

┌─────────────────────────┐
│ ◄ Back to Device        │
├─────────────────────────┤
│ Port: GigabitEthernet0/1│
│                         │
│ Type: 1000BASE-T        │
│ Label: [___________]    │
│ ☐ Management only       │
│                         │
│ PoE: PSE (802.3at)      │
│                         │
│ Connection:             │
│ ○ Not connected         │
│ [Connect to...]         │
└─────────────────────────┘

State Management

• Add selectedPort to layout store or canvas store
• Clear on device deselect
• Clear on escape key

Dependencies

• feat: integrate PortIndicators into RackDevice #250 (PortIndicators integrated with click handlers)

References

• EditPanel: src/lib/components/EditPanel.svelte