add reporting foundation: multipage nav, auth gate, date-range fetch

First increment of the clinical reporting feature (see
docs/requirements-reporting.md and docs/design-reporting.md): moves the
existing live view to pages/1_Live.py, adds a password gate since the
dashboard URL will be shared with the diabetes team, adds
fetch_entries_range/fetch_treatments_range for multi-day report queries,
and adds reporting.py with the core clinical calculations (GMI, %CV,
5-band time-in-range, hypo/hyper event detection per the Battelino et al.
2019 persistence rule). No report pages wired up yet — that's next.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

tests/test_nightscout_client.py

@@ -1,4 +1,4 @@
-from datetime import datetime, timedelta, timezone
+from datetime import date, datetime, timedelta, timezone
 
 import pytest
 
@@ -96,3 +96,41 @@ def pd_isna(value):
     import pandas as pd
 
     return pd.isna(value)
+
+
+def test_fetch_entries_range_filters_to_date_boundaries(monkeypatch):
+    monkeypatch.setenv("NIGHTSCOUT_URL", "https://example.com")
+    monkeypatch.delenv("NIGHTSCOUT_TOKEN", raising=False)
+    monkeypatch.delenv("NIGHTSCOUT_API_SECRET", raising=False)
+
+    payload = [
+        {"date": int(datetime(2026, 1, 15, 12, 0, tzinfo=timezone.utc).timestamp() * 1000), "sgv": 126},
+        {"date": int(datetime(2026, 1, 1, 12, 0, tzinfo=timezone.utc).timestamp() * 1000), "sgv": 90},
+        {"date": int(datetime(2026, 2, 1, 12, 0, tzinfo=timezone.utc).timestamp() * 1000), "sgv": 100},
+    ]
+    monkeypatch.setattr(ns.requests, "get", lambda *a, **k: FakeResponse(payload))
+
+    result = ns.fetch_entries_range(date(2026, 1, 1), date(2026, 1, 31))
+    assert len(result) == 2  # de 1 feb-meting valt buiten het bereik
+    assert list(result.columns) == ["timestamp", "mmol"]
+
+
+def test_fetch_entries_range_handles_empty_response(monkeypatch):
+    monkeypatch.setenv("NIGHTSCOUT_URL", "https://example.com")
+    monkeypatch.setattr(ns.requests, "get", lambda *a, **k: FakeResponse([]))
+
+    result = ns.fetch_entries_range(date(2026, 1, 1), date(2026, 1, 31))
+    assert result.empty
+
+
+def test_fetch_treatments_range_filters_to_date_boundaries(monkeypatch):
+    monkeypatch.setenv("NIGHTSCOUT_URL", "https://example.com")
+    payload = [
+        {"created_at": "2026-01-15T12:00:00Z", "eventType": "Meal Bolus", "insulin": 4.0, "carbs": 40},
+        {"created_at": "2026-02-01T12:00:00Z", "eventType": "Meal Bolus", "insulin": 3.0, "carbs": 30},
+    ]
+    monkeypatch.setattr(ns.requests, "get", lambda *a, **k: FakeResponse(payload))
+
+    result = ns.fetch_treatments_range(date(2026, 1, 1), date(2026, 1, 31))
+    assert len(result) == 1
+    assert result.iloc[0]["insulin"] == pytest.approx(4.0)