Improvements to fitness page

- Data now comes from a calendar
- Hovering in charts shows day info
- Optical enhancements to chart rendering
- Allow setting/showing goal weight
- Allow toggeling between absolute and zoomed in weight axis

calendar.go

@@ -646,6 +646,20 @@ func calendarDayLines(from, to time.Time) map[string]calDayLines {
 		}
 	}
 
+	for key, w := range calendarWeights(s, from, to) {
+		lines := out[key]
+		lines.Weight = strings.ReplaceAll(w, ".", ",") + " kg"
+		out[key] = lines
+	}
+	return out
+}
+
+// calendarWeights reads the weight role for [from, to): one entry per day,
+// keyed by "YYYY-MM-DD", holding the kg value with a '.' decimal separator.
+// Events whose title is not a weight are skipped; several entries on one day:
+// the last edited one wins.
+func calendarWeights(s calendarSettings, from, to time.Time) map[string]string {
+	out := map[string]string{}
 	stamps := map[string]time.Time{}
 	for _, ev := range calendarOccurrences(calendarsDir, s.Weight, from, to) {
 		m := weightTitle.FindStringSubmatch(ev.Summary)
@@ -653,14 +667,11 @@ func calendarDayLines(from, to time.Time) map[string]calDayLines {
 			continue
 		}
 		key := ev.Start.Format("2006-01-02")
-		// Several entries on one day: the last edited one wins.
 		if prev, ok := stamps[key]; ok && ev.Stamp.Before(prev) {
 			continue
 		}
 		stamps[key] = ev.Stamp
-		lines := out[key]
-		lines.Weight = strings.ReplaceAll(m[1], ".", ",") + " kg"
-		out[key] = lines
+		out[key] = strings.ReplaceAll(m[1], ",", ".")
 	}
 	return out
 }