feat(fork)!: remove all frontend Enterprise-Edition code (community build)

Strip the proprietary client EE so the fork ships a clean community/AGPL
edition, mirroring Forkmost. Delete apps/client/src/ee (201 files) and
packages/ee, and patch every consumer that imported from @/ee/*.

- gate-out EE features (useHasFeature -> false): API keys, SSO, MFA, SCIM,
  audit logs, AI / AI-chat, templates, page permissions, page verification,
  comment resolution, trash retention, viewer comments
- drop cloud/billing/trial/entitlement/posthog flows; sign-in is now
  email+password only (no SSO/LDAP/cloud)
- remove EE routes from App.tsx and EE entries from sidebars/settings nav
- restore the community page-share button (ShareModal) that the EE
  PageShareModal used to provide
- remove the dead "Attachments" search filter, dead MFA navigation and
  orphaned route constants

Client type-checks clean; full `pnpm build` is green for all three projects.

apps/client/src/lib/api-client.ts

@@ -68,8 +68,6 @@ function redirectToLogin() {
     APP_ROUTE.AUTH.SIGNUP,
     APP_ROUTE.AUTH.FORGOT_PASSWORD,
     APP_ROUTE.AUTH.PASSWORD_RESET,
-    APP_ROUTE.AUTH.MFA_CHALLENGE,
-    APP_ROUTE.AUTH.MFA_SETUP_REQUIRED,
     "/invites",
   ];
   if (!exemptPaths.some((path) => window.location.pathname.startsWith(path))) {