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/app/modules/content/models.py

@@ -0,0 +1,27 @@
+from __future__ import annotations
+
+from datetime import UTC, datetime
+from uuid import uuid4
+
+from sqlalchemy import DateTime, ForeignKey, String, Text
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.db.base import Base
+
+
+class ContentPage(Base):
+    __tablename__ = "content_pages"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=lambda: str(uuid4()))
+    slug: Mapped[str] = mapped_column(String(120), unique=True, nullable=False, index=True)
+    title: Mapped[str] = mapped_column(String(255), nullable=False)
+    body: Mapped[str] = mapped_column(Text, nullable=False)
+    status: Mapped[str] = mapped_column(String(16), nullable=False, default="draft", index=True)
+    author_id: Mapped[str | None] = mapped_column(String(36), ForeignKey("users.id"), nullable=True)
+    published_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        nullable=False,
+        default=lambda: datetime.now(UTC),
+        onupdate=lambda: datetime.now(UTC),
+    )