feat(admin): finalizing modular refactoring with testing suite and UI polish

backend/tests/test_admin.py

@@ -0,0 +1,35 @@
+import pytest
+
+def test_get_backups(client):
+    response = client.get("/admin/db/backups")
+    assert response.status_code == 200
+    assert isinstance(response.json(), list)
+
+def test_db_settings_workflow(client):
+    # GET settings
+    response = client.get("/admin/db/settings")
+    assert response.status_code == 200
+    data = response.json()
+    assert "retention_count" in data
+    
+    # PATCH settings
+    new_settings = {
+        "retention_count": 25,
+        "schedule_hour": 5,
+        "schedule_freq_days": 2
+    }
+    response = client.patch("/admin/db/settings", json=new_settings)
+    assert response.status_code == 200
+    assert response.json()["retention_count"] == 25
+    
+    # Verify persistence
+    response = client.get("/admin/db/settings")
+    assert response.json()["retention_count"] == 25
+
+def test_ai_config(client):
+    response = client.get("/admin/db/settings/ai")
+    assert response.status_code == 200
+    data = response.json()
+    assert "active_provider" in data
+    assert "providers" in data
+    assert len(data["providers"]) == 2