fix(statistics): feeding totals per unit instead of adding litres to kilograms

The feeding statistics summed every amount regardless of its unit, so
5 l syrup and 2 kg fondant showed as 7. The API now also returns byUnit
(units normalised: "L" = "l"), the old fields stay for compatibility,
and the statistics page shows one list per unit.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

ApiCore-Backend/src/statistics/statistics.service.spec.ts

@@ -212,5 +212,25 @@ describe('StatisticsService', () => {
       expect(result.byColony).toEqual({ c1: 8, c2: 2 });
       expect(result.bySeason).toEqual({ '2025': 8, '2024': 2 });
     });
+
+    it('never adds litres and kilograms together', async () => {
+      prisma.feeding.findMany.mockResolvedValueOnce([
+        { colonyId: 'c1', date: new Date('2025-09-01'), amount: 5, unit: 'l' },
+        { colonyId: 'c1', date: new Date('2025-09-15'), amount: 2, unit: 'kg' },
+        {
+          colonyId: 'c1',
+          date: new Date('2025-10-01'),
+          amount: 1,
+          unit: ' L ',
+        },
+      ]);
+
+      const result = await service.feeding();
+
+      expect(result.byUnit).toEqual({
+        l: { byColony: { c1: 6 }, bySeason: { '2025': 6 } },
+        kg: { byColony: { c1: 2 }, bySeason: { '2025': 2 } },
+      });
+    });
   });
 });

ApiCore-Backend/src/statistics/statistics.service.ts

@@ -206,15 +206,27 @@ export class StatisticsService {
       select: { colonyId: true, date: true, amount: true, unit: true },
     });
 
+    // Litres and kilograms cannot be added up: totals are kept per unit
+    // (byUnit). byColony/bySeason stay for older clients and are only
+    // meaningful when a single unit is in use.
     const byColony: Record<string, number> = {};
     const bySeason: Record<string, number> = {};
+    const byUnit: Record<
+      string,
+      { byColony: Record<string, number>; bySeason: Record<string, number> }
+    > = {};
     for (const feeding of feedings) {
+      const year = feeding.date.getFullYear().toString();
+      const unit = feeding.unit.trim().toLowerCase() || 'ohne Einheit';
       byColony[feeding.colonyId] =
         (byColony[feeding.colonyId] ?? 0) + feeding.amount;
-      const year = feeding.date.getFullYear().toString();
       bySeason[year] = (bySeason[year] ?? 0) + feeding.amount;
+      const totals = (byUnit[unit] ??= { byColony: {}, bySeason: {} });
+      totals.byColony[feeding.colonyId] =
+        (totals.byColony[feeding.colonyId] ?? 0) + feeding.amount;
+      totals.bySeason[year] = (totals.bySeason[year] ?? 0) + feeding.amount;
     }
 
-    return { byColony, bySeason };
+    return { byColony, bySeason, byUnit };
   }
 }

ApiCore-Frontend/src/app/(app)/statistics/page.tsx

@@ -293,25 +293,35 @@ function FeedingStatsPanel({ colonyLabels }: { colonyLabels: Map<string, string>
 
   return (
     <QueryState query={query} what="Futterdaten">
-      {(data) => (
+      {(data) => {
+        // One block per unit: litres and kilograms are never added up.
+        const units = Object.entries(
+          data.byUnit ?? { [FEED_UNIT]: { byColony: data.byColony, bySeason: data.bySeason } },
+        );
+        return (
           <div className="flex flex-col gap-4">
             <PanelHint>
-            Summe der eingetragenen Futtermengen in Liter bzw. kg, so wie sie bei der Fütterung
-            erfasst wurden.
+              Summe der eingetragenen Futtermengen, getrennt nach Einheit – so wie sie bei der
+              Fütterung erfasst wurden.
             </PanelHint>
+            {units.length === 0 ? (
+              <p className="text-sm text-muted-foreground">Noch keine Fütterungen erfasst.</p>
+            ) : null}
+            {units.map(([unit, totals]) => (
+              <div key={unit} className="flex flex-col gap-4">
                 <Card>
                   <CardHeader>
-              <CardTitle>Futterverbrauch pro Volk</CardTitle>
+                    <CardTitle>Futterverbrauch pro Volk ({unit})</CardTitle>
                   </CardHeader>
                   <CardContent>
                     <StatBarList
-                items={Object.entries(data.byColony)
+                      items={Object.entries(totals.byColony)
                         .sort(([, a], [, b]) => b - a)
                         .slice(0, 10)
                         .map(([colonyId, value]) => ({
                           label: colonyLabels.get(colonyId) ?? colonyId,
                           value,
-                    unit: FEED_UNIT,
+                          unit,
                         }))}
                       formatValue={kg}
                       emptyText="Noch keine Fütterungen erfasst."
@@ -320,14 +330,14 @@ function FeedingStatsPanel({ colonyLabels }: { colonyLabels: Map<string, string>
                 </Card>
                 <Card>
                   <CardHeader>
-              <CardTitle>Futterverbrauch pro Saison</CardTitle>
+                    <CardTitle>Futterverbrauch pro Saison ({unit})</CardTitle>
                   </CardHeader>
                   <CardContent>
                     <StatBarList
-                items={sortedRecordEntries(data.bySeason).map(([year, value]) => ({
+                      items={sortedRecordEntries(totals.bySeason).map(([year, value]) => ({
                         label: year,
                         value,
-                  unit: FEED_UNIT,
+                        unit,
                       }))}
                       formatValue={kg}
                       emptyText="Noch keine Fütterungen erfasst."
@@ -335,7 +345,10 @@ function FeedingStatsPanel({ colonyLabels }: { colonyLabels: Map<string, string>
                   </CardContent>
                 </Card>
               </div>
-      )}
+            ))}
+          </div>
+        );
+      }}
     </QueryState>
   );
 }

ApiCore-Frontend/src/lib/statistics/types.ts

@@ -48,4 +48,6 @@ export interface HoneyStats {
 export interface FeedingStats {
   byColony: Record<string, number>;
   bySeason: Record<string, number>;
+  /** Totals per unit ("l", "kg", ...) - units are never added together. */
+  byUnit?: Record<string, { byColony: Record<string, number>; bySeason: Record<string, number> }>;
 }