[UI] Add Privacy section in Settings

[LeGeRyChEeSe]

Description

Add a "Privacy" section in the Settings screen allowing the user to change their consent at any time.

File to modify

• Existing Settings screen (search for SettingsScreen.kt or similar)

Expected UI

Settings (gear icon)
  └── Privacy (Card)
        └── Anonymous Statistics
              ├── Description: "Help improve VRHub by sharing anonymous usage data..."
              ├── Toggle Switch: "Share anonymous statistics"
              └── (if enabled) Green text: "✓ Your data is being shared anonymously"

Behavior

• The Switch reflects ConsentPreferences.consentEnabled state (collected via stateIn in ViewModel)
• onCheckedChange triggers ConsentPreferences.setConsentEnabled(...) and StatsCollector.updateConsent() to sync with the server
• On disable: cancel StatsCollectionWorker
• On enable: enqueue StatsCollectionWorker

Reference

• docs/CLIENT_SPEC.md §6
• docs/CLIENT_IMPLEMENTATION.md §6