Fix unit conversion: EL/TL/Prise/Bund support, proper kg↔g deduction

units.ts:
- EL/Esslöffel → 15ml, TL/Teelöffel → 5ml, Prise → 0.5g, Bund → 1 Stück
- Now "2 EL Olivenöl" correctly matches inventory "500 ml Olivenöl"

/api/recipes/cook:
- Full unit conversion before deduction (was comparing raw numbers)
- 1kg recipe vs 1000g inventory now correctly deducts 1000g
- Convert back to original unit after deduction for DB consistency

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: JiroMusik

server.ts

@@ -1872,16 +1872,41 @@ app.post('/api/recipes/cook', (req, res) => {
             db.prepare('UPDATE items SET quantity = ? WHERE id = ?').run(newQty, item.id);
             item.quantity = newQty;
             deducted.push({ ...item, quantity_deducted: pctDeduct });
-          } else if (item.quantity >= ing.amount) {
-            const newQty = item.quantity - ing.amount;
-            db.prepare('UPDATE items SET quantity = ? WHERE id = ?').run(newQty, item.id);
-            item.quantity = newQty; // update in-memory for subsequent matches
-            deducted.push({ ...item, quantity_deducted: ing.amount });
           } else {
-            db.prepare('UPDATE items SET quantity = 0 WHERE id = ?').run(item.id);
-            deducted.push({ ...item, quantity_deducted: item.quantity });
-            missing.push(`${ing.name} (Fehlt: ${ing.amount - item.quantity} ${ing.unit || item.unit || ''})`.trim());
-            item.quantity = 0;
+            // Convert both to smallest unit for correct comparison (e.g. 1kg vs 1000g)
+            const reqSmall = convertToSmallestUnit(ing.amount, ing.unit || item.unit);
+            const invSmall = convertToSmallestUnit(item.quantity, item.unit);
+
+            if (reqSmall.unit === invSmall.unit) {
+              // Units compatible — deduct with conversion
+              if (invSmall.amount >= reqSmall.amount) {
+                const remaining = invSmall.amount - reqSmall.amount;
+                // Convert back to original unit
+                const newQty = (remaining / invSmall.amount) * item.quantity;
+                db.prepare('UPDATE items SET quantity = ? WHERE id = ?').run(newQty, item.id);
+                item.quantity = newQty;
+                deducted.push({ ...item, quantity_deducted: ing.amount });
+              } else {
+                db.prepare('UPDATE items SET quantity = 0 WHERE id = ?').run(item.id);
+                deducted.push({ ...item, quantity_deducted: item.quantity });
+                const missingSmall = reqSmall.amount - invSmall.amount;
+                missing.push(`${ing.name} (Fehlt: ${Math.round(missingSmall * 100) / 100} ${reqSmall.unit})`.trim());
+                item.quantity = 0;
+              }
+            } else {
+              // Units incompatible (shouldn't happen often) — try raw deduction as fallback
+              if (item.quantity >= ing.amount) {
+                const newQty = item.quantity - ing.amount;
+                db.prepare('UPDATE items SET quantity = ? WHERE id = ?').run(newQty, item.id);
+                item.quantity = newQty;
+                deducted.push({ ...item, quantity_deducted: ing.amount });
+              } else {
+                db.prepare('UPDATE items SET quantity = 0 WHERE id = ?').run(item.id);
+                deducted.push({ ...item, quantity_deducted: item.quantity });
+                missing.push(`${ing.name} (Fehlt: ${ing.amount - item.quantity} ${ing.unit || item.unit || ''})`.trim());
+                item.quantity = 0;
+              }
+            }
           }
         } else {
           missing.push(ing.name);

server/utils/units.ts

@@ -13,6 +13,12 @@ export const convertToSmallestUnit = (amount: number, unit: string): { amount: n
   const norm = normalizeUnit(unit);
   if (norm === 'kg') return { amount: amount * 1000, unit: 'g' };
   if (norm === 'l') return { amount: amount * 1000, unit: 'ml' };
+  // Cooking units → approximate g/ml conversion
+  const u = unit.toLowerCase().trim();
+  if (u === 'el' || u === 'esslöffel' || u === 'tbsp') return { amount: amount * 15, unit: 'ml' };
+  if (u === 'tl' || u === 'teelöffel' || u === 'tsp') return { amount: amount * 5, unit: 'ml' };
+  if (u === 'prise' || u === 'pinch') return { amount: amount * 0.5, unit: 'g' };
+  if (u === 'bund' || u === 'bunch') return { amount: amount, unit: 'Stück' };
   return { amount, unit: norm };
 };