Move auth server from federation to account

Account is now the OAuth authorization server with magic link login,
OAuth2 authorize endpoint, SSO logout, and session management.

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

blog/models/__init__.py

@@ -0,0 +1,14 @@
+from .ghost_content import Post, Author, Tag, PostAuthor, PostTag, PostLike
+from .snippet import Snippet
+from .tag_group import TagGroup, TagGroupTag
+
+# Shared models — canonical definitions live in shared/models/
+from shared.models.ghost_membership_entities import (
+    GhostLabel, UserLabel,
+    GhostNewsletter, UserNewsletter,
+    GhostTier, GhostSubscription,
+)
+from shared.models.menu_item import MenuItem
+from shared.models.kv import KV
+from shared.models.magic_link import MagicLink
+from shared.models.user import User