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/core/database.py

@@ -0,0 +1,50 @@
+from __future__ import annotations
+
+from collections.abc import Generator
+from contextlib import contextmanager
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import Session, sessionmaker
+from sqlalchemy.pool import StaticPool
+
+from app.core.config import settings
+
+_connect_args: dict[str, object] = {}
+_engine_kwargs: dict[str, object] = {
+    "pool_pre_ping": True,
+    "future": True,
+    "pool_size": 5,
+    "max_overflow": 10,
+    "pool_recycle": 1800,
+}
+
+if settings.database_url.startswith("sqlite"):
+    _connect_args["check_same_thread"] = False
+    _engine_kwargs["poolclass"] = StaticPool
+    _engine_kwargs.pop("pool_size", None)
+    _engine_kwargs.pop("max_overflow", None)
+    _engine_kwargs.pop("pool_recycle", None)
+
+engine = create_engine(settings.database_url, connect_args=_connect_args, **_engine_kwargs)
+SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, future=True)
+
+
+@contextmanager
+def session_scope() -> Generator[Session, None, None]:
+    session = SessionLocal()
+    try:
+        yield session
+        session.commit()
+    except Exception:
+        session.rollback()
+        raise
+    finally:
+        session.close()
+
+
+def get_db() -> Generator[Session, None, None]:
+    session = SessionLocal()
+    try:
+        yield session
+    finally:
+        session.close()