docs: update architecture with bootstrap phases, scopes, branding

- CLAUDE.md: add bootstrap phase listing, document 13 scopes (10
  platform + 3 server), server role mapping via scope claim, admin
  console access, sign-in branding
- Mark server-role-mapping and logto-admin-branding specs as implemented

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/superpowers/specs/2026-04-06-logto-admin-and-branding-design.md

@@ -1,4 +1,4 @@
-# Logto Admin Credentials + Sign-In Branding
+# Logto Admin Credentials + Sign-In Branding — IMPLEMENTED
 
 ## Problem
 

docs/superpowers/specs/2026-04-06-server-role-mapping-design.md

@@ -1,4 +1,4 @@
-# Server Role Mapping via Logto Scopes
+# Server Role Mapping via Logto Scopes — IMPLEMENTED
 
 ## Problem