feat: Grav 2.0 compat — flex accounts/pages, api.super permission

- accounts.type: flex (required by admin2 API)
- pages.type: flex (required for admin2 pages API)
- Add access.api.super + api.access to mischa account (admin2 uses api.* permissions, not admin.*)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

config/security.yaml

@@ -1 +1 @@
-salt: lsUHWFkCwvGZrL
+{  }

config/system.yaml

@@ -31,7 +31,7 @@ home:
   alias: /trips/japan-korea-2026/dailies
   hide_in_urls: false
 pages:
-  type: regular
+  type: flex
   dirs:
     - 'page://'
   theme: intotheeast
@@ -221,7 +221,7 @@ http:
   verify_peer: true
   verify_host: true
 accounts:
-  type: regular
+  type: flex
   storage: file
   avatar: gravatar
 flex: