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/audit_log.py

@@ -0,0 +1,49 @@
+from __future__ import annotations
+
+import json
+from datetime import UTC, datetime
+from pathlib import Path
+from typing import Any
+
+from app.core.config import settings
+
+
+def _audit_path() -> Path:
+    return Path(settings.admin_audit_log_path)
+
+
+def write_audit_event(
+    action: str,
+    actor_user_id: str,
+    actor_email: str,
+    details: dict[str, Any] | None = None,
+) -> None:
+    payload = {
+        "timestamp": datetime.now(UTC).isoformat(),
+        "action": action,
+        "actor_user_id": actor_user_id,
+        "actor_email": actor_email,
+        "details": details or {},
+    }
+    path = _audit_path()
+    path.parent.mkdir(parents=True, exist_ok=True)
+    with path.open("a", encoding="utf-8") as file:
+        file.write(json.dumps(payload, ensure_ascii=False))
+        file.write("\n")
+
+
+def read_audit_events(limit: int = 200) -> list[dict[str, Any]]:
+    path = _audit_path()
+    if not path.exists():
+        return []
+    lines = path.read_text(encoding="utf-8").splitlines()
+    tail = lines[-limit:]
+    events: list[dict[str, Any]] = []
+    for line in tail:
+        if not line.strip():
+            continue
+        try:
+            events.append(json.loads(line))
+        except json.JSONDecodeError:
+            continue
+    return list(reversed(events))