Add vault stats command and API endpoint

src/tests/test_api_profile_stats.py

@@ -0,0 +1,13 @@
+from test_api import client
+
+
+def test_profile_stats_endpoint(client):
+    cl, token = client
+    stats = {"total_entries": 1}
+    # monkeypatch set _pm.get_profile_stats after client fixture started
+    import seedpass.api as api
+
+    api._pm.get_profile_stats = lambda: stats
+    res = cl.get("/api/v1/stats", headers={"Authorization": f"Bearer {token}"})
+    assert res.status_code == 200
+    assert res.json() == stats