Collectives P1: participation landing (ES/EN), group tree, room provisioning APIs

- 030: groups.parent_id tree + kind discriminator + group_rooms mapping
- /collectives module: create/tree/join APIs, MatrixProvisioner (open room
  public+federated, closed room E2EE-at-creation, onboarding room), NullProvisioner
  fail-soft when ARCHIVE_PROVISIONER_* unset
- web root becomes the public participation manual (ES-first + EN toggle,
  three paths: join by invite, start collective, solo account)
- participation manual content in core

apps/web/next.config.mjs

@@ -1,9 +1,9 @@
 /** @type {import('next').NextConfig} */
 const nextConfig = {
   reactStrictMode: true,
-  async redirects() {
-    return [{ source: "/", destination: "/streams", permanent: false }];
-  },
+  // The app root ("/") is the public participation-manual landing page
+  // (collectives P1): no redirect — see src/app/page.tsx. Signed-in visitors
+  // are sent to /streams client-side so the manual stays reachable.
   async rewrites() {
     const api = (process.env.NEXT_PUBLIC_API_URL ?? "http://localhost:3000").replace(/\/$/, "");
     return [{ source: "/media-control/preview/:path*", destination: `${api}/media-control/preview/:path*` }];