docs: add dedicated telemetry documentation page

[Angelmmiguel]

Extracts telemetry documentation from user-settings.mdx into a dedicated telemetry.mdx page with expanded coverage of privacy practices, data collection, and opt-out methods.

Changes

• Created new rover/config/telemetry.mdx with comprehensive telemetry documentation:
  • Why telemetry is collected
  • How privacy is protected (anonymous UUID, no personal data)
  • What data is collected per command
  • What is never collected (descriptions, code, secrets)
  • Three methods to disable telemetry (environment variable, global store config, legacy marker file)
  • Platform-specific paths for macOS/Linux and Windows
• Removed telemetry section from user-settings.mdx and added link to new page
• Added telemetry link to project-config.mdx Next Steps section

Notes

The documentation now reflects the current implementation where telemetry settings are stored in the global store (~/.rover/config/rover.json) rather than the legacy location (~/.config/rover/). All three disable methods are documented with the legacy marker file clearly marked as such.