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]>

.env.example

@@ -10,3 +10,8 @@ NIGHTSCOUT_TOKEN=
 
 # Optie 2: het klassieke "API secret" van je Nightscout-instantie.
 # NIGHTSCOUT_API_SECRET=
+
+# Wachtwoord voor toegang tot het dashboard (de URL wordt straks gedeeld met
+# het diabetesteam). Zet hier een sha256-hash, NIET het wachtwoord zelf:
+#   python -c "import hashlib; print(hashlib.sha256(b'jouw-wachtwoord').hexdigest())"
+DASHBOARD_PASSWORD_HASH=