Update admin theme/layout and refresh README details.

Align the project baseline with the latest admin interface styling and layout structure while documenting setup and usage updates in README.

apps/api/migrations/versions/20260711_0002_seed_data.py

@@ -0,0 +1,33 @@
+"""seed admin and demo content
+
+Revision ID: 20260711_0002
+Revises: 20260711_0001
+Create Date: 2026-07-11 14:05:00
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+
+revision: str = "20260711_0002"
+down_revision: Union[str, None] = "20260711_0001"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Demo users and CMS pages are seeded on API startup (app.main lifespan → run_seed)
+    # after all schema migrations, including is_superuser (20260714_0003).
+    pass
+
+
+def downgrade() -> None:
+    from sqlalchemy import delete
+
+    from app.core.database import session_scope
+    from app.modules.content.models import ContentPage
+    from app.modules.users.models import User
+
+    with session_scope() as db:
+        db.execute(delete(ContentPage).where(ContentPage.slug.in_(["about", "privacy", "terms"])))
+        db.execute(delete(User).where(User.email == "admin@compton.example"))