Remove referrals feature while preserving existing referral data

Strip the /refer-friends CLI command, web referral pages, affiliate
sponsee routes, and one-time referral redemption API. Simplify the
profile referrals section to a read-only list of who you referred.
Keep DB schema, legacy monthly bonus grants, and the GrantType enum
so historical referrals continue to pay out.

Restore creator attribution for freebuff only: /get-started already
accepts ?referrer=<name> and persists it; /onboard fires a
FREEBUFF_REFERRER_ATTRIBUTED PostHog event with \$set_once on first
visit post-login. /onboard now redirects logged-out visitors to
/get-started (or /login when an auth_code is present) and greets
logged-in users with an optional "{Name} invited you to try Freebuff!"
header. Fixes a pre-existing bug where auth_code was dropped when
/onboard redirected unauthenticated users.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: jahooma

cli/src/__tests__/helpers/mock-api-client.ts

@@ -13,7 +13,6 @@ export interface MockApiClientOverrides {
   usage?: ReturnType<typeof mock>
   loginCode?: ReturnType<typeof mock>
   loginStatus?: ReturnType<typeof mock>
-  referral?: ReturnType<typeof mock>
   publish?: ReturnType<typeof mock>
   logout?: ReturnType<typeof mock>
   feedback?: ReturnType<typeof mock>
@@ -54,8 +53,6 @@ export const createMockApiClient = (
     mock(defaultOkResponse)) as CodebuffApiClient['loginCode'],
   loginStatus: (overrides.loginStatus ??
     mock(defaultOkResponse)) as CodebuffApiClient['loginStatus'],
-  referral: (overrides.referral ??
-    mock(defaultOkResponse)) as CodebuffApiClient['referral'],
   publish: (overrides.publish ??
     mock(defaultOkResponse)) as CodebuffApiClient['publish'],
   logout: (overrides.logout ??