WebUI: human-readable labels and section titles/descriptors in Settings

[lonix]

Problem

The Settings page presents each row by its raw dotted key — voicetracking.enabled, voicechannels.lobby.offlinename — which is fine for developers but unfriendly for the operators we expect to use this UI. Section headers are equally bare: the renderer (src/web/admin-views.ts:254) emits <h2>voicechannels</h2> — a slug, no descriptor.

settingsMetadata (src/services/config-schema.ts:220-223) already carries a per-key description, but the dotted key is still the primary label and categories have no human-readable title at all.

Proposed change

Extend the per-key and per-category metadata:

export interface SettingMetadata {
  label: string;        // NEW. Human-readable, e.g., "Voice Tracking enabled".
  description: string;  // (existing) one-line help text.
  category: string;     // (existing) machine slug.
}

export interface CategoryMetadata {
  title: string;        // NEW. e.g., "Voice Tracking".
  description: string;  // NEW. e.g., "Time-in-voice tracking, leaderboards, last-seen, …".
}

export const categoryMetadata: Record<string, CategoryMetadata> = { … };

Rendering changes in renderSettingsPage / renderSettingInput:

• Section header: <h2>{title}</h2><p class="muted">{description}</p> instead of <h2>{category}</h2>.
• Per-row primary: <strong>{label}</strong> (e.g., "Voice Tracking enabled").
• Per-row secondary: the existing description as the help text.
• Per-row tertiary, muted, right-aligned: the raw key (voicetracking.enabled) as a small <code> for technical reference — devs and bug reporters still need to see it.

Acceptance

• Every key has a non-empty label.
• Every category has a non-empty title and description.
• Settings page renders human labels as the primary text; raw dotted keys are visible but de-emphasized.
• Existing tests still pass; new test asserts the metadata maps cover every key in ConfigSchema (no orphans).

Notes

• Discussed in conversation: per the user, "Voice Tracking enabled" reads better than voicetracking.enabled. We should have both a "name" and a "keyname" for these settings.
• Prerequisite for WebUI: dropdown selectors for channel/category/role config keys (replace freetext) #439 — that issue's type hint lands naturally in SettingMetadata next to label.