Add capability-specific config UI

[srgvg]

Context

5 backend endpoints exist for capability-specific device configuration, but there is no API module or UI for these features. This requires creating a new API module and integrating it into the device config UI.

Backend Endpoints (no frontend coverage)

• Relay configuration settings
• Dimming configuration settings
• Roller/cover configuration settings
• Power metering configuration settings
• Device authentication settings

Work Required

1. Create new API module: ui/src/api/capabilityConfig.ts
2. Create or extend store for capability configs
3. Add UI components/sections in device config pages
4. Wire up API calls to display and edit capability-specific settings

Affected Files

• New: ui/src/api/capabilityConfig.ts
• ui/src/pages/DeviceConfigPage.vue
• ui/src/pages/DeviceDetailPage.vue

Acceptance Criteria

• API module created with functions for all 5 capability endpoints
• Relay config UI shows and edits relay settings
• Dimming config UI shows and edits dimmer settings
• Roller config UI shows and edits roller/cover settings
• Power metering config UI displays metering settings
• Device auth settings UI allows credential management
• Capability sections only shown for devices that have the capability