fix(frontend): label every settings slider

[voltcrash]

Description

Settings range controls had no accessible names, and background-filter labels were plain text.

Add a required Slider label, optional control ID, descriptive names for all six consumers and component-owned IDs/native labels for background filters. Reactive label updates remain supported.

Validation

• Slider accessibility: 6 passed (failed before the fix): all names, visible label associations and reactive updates.
• Custom setting resets: 7 passed.
• Staged formatting and lint/type checks passed.