Fix Google Calendar TimeMin using server time instead of display timezone

GetUpcomingEvents built its TimeMin cutoff from raw time.Now() (server/UTC
time), not the start of today in the configured display timezone. Google's
API filters TimeMin against each event's END time (exclusive), so for a
UTC-10 display timezone (Pacific/Honolulu) that cutoff landed mid-afternoon
the PREVIOUS Hawaii-local day, not midnight of the actual display day.

Confirmed against live data before fixing, not assumed: the cached
calendar_events table's earliest row was "2026-08-05 15:00:00-10:00" --
exactly the mid-afternoon-yesterday skew this bug produces -- with a
complete gap for all of 2026-08-06 (today). This is what caused two
symptoms reported against the widget: already-ended-today events missing
entirely (never fetched into the cache in the first place, not a
client-side rendering bug -- the 2026-08-05 Android "past events" feature
was built correctly but had nothing to render) and the tomorrow section
appearing empty (same skewed data window scrambling the day-bucketing
downstream).

Fix: compute TimeMin from time.Now().In(displayTZ)'s start-of-day instead.
Added TestGetUpcomingEvents_TimeMinIsStartOfTodayInDisplayTimezone, which
asserts the actual outgoing timeMin query parameter is midnight-in-tz and
lands on today's date -- verified it catches the regression by reverting
to raw time.Now() against a real backup and confirming the exact failure
mode (captured timeMin = mid-afternoon the day before), then restored.

go test ./... -race is green. Deployed. Note: the calendar cache only
refreshes when the web dashboard is visited (aggregateData) -- the widget's
own refresh only re-reads the DB cache, never triggers a live Calendar
resync -- so the currently-cached stale data needs one dashboard visit to
actually reflect this fix, not just the deploy.

1 files changed, 44 insertions, 0 deletions

diff --git a/internal/api/google_calendar_test.go b/internal/api/google_calendar_test.go
index 3cf0dbd..92fdea3 100644
--- a/internal/api/google_calendar_test.go
+++ b/internal/api/google_calendar_test.go
@@ -272,3 +272,47 @@ func TestGetUpcomingEvents_APIError_ReturnsEmptyNotError(t *testing.T) {
 		t.Errorf("expected 0 events on API error, got %d", len(events))
 	}
 }
+
+// Regression test for the 2026-08-06 incident: GetUpcomingEvents used
+// time.Now() (server/UTC time) as TimeMin instead of the start of today in
+// the display timezone. Google's API filters TimeMin against each event's
+// END time, so for Pacific/Honolulu (UTC-10) that cutoff landed mid-afternoon
+// the PREVIOUS Hawaii-local day, not midnight of the actual display day --
+// silently excluding every already-ended-today event from ever being
+// fetched into the cache, and skewing the whole today/tomorrow split
+// downstream by the same ~10h gap. This would have caught it: raw
+// time.Now() fails both assertions below for any negative-UTC-offset zone.
+func TestGetUpcomingEvents_TimeMinIsStartOfTodayInDisplayTimezone(t *testing.T) {
+	var capturedTimeMin string
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		capturedTimeMin = r.URL.Query().Get("timeMin")
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"kind":"calendar#events","items":[]}`))
+	}))
+	defer server.Close()
+
+	tz, err := time.LoadLocation("Pacific/Honolulu")
+	if err != nil {
+		t.Fatalf("failed to load Pacific/Honolulu: %v", err)
+	}
+	client := newTestGoogleCalendarClient(t, server, []string{"primary"}, tz)
+	if _, err := client.GetUpcomingEvents(context.Background(), 10); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	got, err := time.Parse(time.RFC3339, capturedTimeMin)
+	if err != nil {
+		t.Fatalf("captured timeMin %q isn't valid RFC3339: %v", capturedTimeMin, err)
+	}
+	gotInTZ := got.In(tz)
+
+	if gotInTZ.Hour() != 0 || gotInTZ.Minute() != 0 || gotInTZ.Second() != 0 {
+		t.Errorf("timeMin = %v (in %s), want midnight", gotInTZ, tz)
+	}
+
+	nowInTZ := time.Now().In(tz)
+	if gotInTZ.Year() != nowInTZ.Year() || gotInTZ.YearDay() != nowInTZ.YearDay() {
+		t.Errorf("timeMin day = %s, want today (%s) in %s",
+			gotInTZ.Format("2006-01-02"), nowInTZ.Format("2006-01-02"), tz)
+	}
+}