feat: interface configuration in Add Device form

[ggfevans]

Parent Epic

Part of #71 (Network Interface Visualization and Connectivity)

Summary

Add interface configuration to the Add Device dialog, balancing simplicity for casual users with power for advanced users.

Problem Statement

• Casual users: just want a colored box
• Power users: want full interface config upfront
• Too complex = frustrating; too simple = limiting

Proposed Solution: Progressive Disclosure

1. Quick Add (default): Name, height, category, color only
2. Advanced Toggle: Expands to show interface configuration
3. Template Selection: "Use template: Cisco 9300-48P" → auto-fill

Acceptance Criteria

• Add "Show advanced options" toggle
• When expanded, show interface configuration
• Quick interface add (count + type)
• Template dropdown (if templates exist)
• Remember preference (localStorage)

UI Design

┌─────────────────────────────────┐
│ Add Device                      │
├─────────────────────────────────┤
│ Name: [___________________]     │
│ Height: [2] U                   │
│ Category: [Network ▼]           │
│ Color: [■ #3b82f6]              │
│                                 │
│ ☐ Show advanced options         │
│                                 │
│ ┌─ Advanced ───────────────────┐│
│ │ Interfaces:                  ││
│ │ [24] × [1000base-t ▼]        ││
│ │ [Add more...]                ││
│ │                              ││
│ │ Or use template:             ││
│ │ [Select template... ▼]       ││
│ └──────────────────────────────┘│
│                                 │
│ [Cancel]              [Add]     │
└─────────────────────────────────┘

Dependencies

• feat: expand InterfaceTemplate type and Zod schema #247 (InterfaceTemplate schema)

References

• Add Device dialog: src/lib/components/AddDeviceDialog.svelte