feat: Add generic 'Other' hardware type for user-defined devices (#244)

[mavnezz]

Summary

Adds a generic "Other" hardware type that allows users to document specialized equipment that doesn't fit into existing categories (e.g. radio infrastructure, interoperability bridges, alternative power distribution, serial/RF data solutions, microwave radio systems).

Closes #244

Changes

• Domain model: New Other class with Model and Description fields
• Use cases: UpdateOtherUseCase, DescribeOtherUseCase, OtherHardwareReportUseCase
• YAML persistence: Registered in serializer/deserializer type discriminators
• JSON schema: Added other definition to schema.v2.json
• UI: OtherCardComponent (detail view with edit/rename/clone/delete) and OtherListPage at /other/list
• Navigation: Added "Other" link to hardware tree subnav

YAML Example

- kind: Other
  name: unifi-radio-01
  model: Building Bridge XG
  description: Microwave radio bridge for site-to-site connectivity