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/tests/modules/auth/test_security.py

@@ -0,0 +1,26 @@
+from app.core.security import (
+    create_access_token,
+    decode_access_token,
+    generate_refresh_token,
+    hash_password,
+    hash_refresh_token,
+    verify_password,
+)
+
+
+def test_password_hashing_roundtrip():
+    hashed = hash_password("Strong123")
+    assert verify_password("Strong123", hashed) is True
+
+
+def test_access_token_encode_decode():
+    token = create_access_token("u1", "user", False)
+    payload = decode_access_token(token)
+    assert payload["sub"] == "u1"
+    assert payload["role"] == "user"
+    assert payload["is_superuser"] is False
+
+
+def test_refresh_token_hashing():
+    token = generate_refresh_token()
+    assert hash_refresh_token(token) == hash_refresh_token(token)