* Add Discord account linking from settings page
Adds a "Connect Discord" button in the Account settings section that
triggers BetterAuth's linkSocial flow to attach a Discord account to
an existing user without requiring a sign-out/sign-in. After the OAuth
callback, the ?section= URL param returns the user to the Account tab.
The Notifications toggle was already gated on Discord being linked.
https://claude.ai/code/session_01UerTpTuBWjreTNEns8srkp
* Fix Discord linking error handling and section routing issues
- Reset linkingDiscord state and show error message when linkSocial throws,
so users can retry if the OAuth flow fails
- Move VALID_SECTION_IDS to module level and derive it from SECTIONS to
avoid per-render allocation and prevent the two from drifting out of sync
- Remove premature SectionId cast before the allowlist validation in
the ?section= URL param handling
- Add tests for loading state and error recovery in AccountSection
Fixes#455https://claude.ai/code/session_01UerTpTuBWjreTNEns8srkp
---------
Co-authored-by: Claude <noreply@anthropic.com>
