feat: MVP 3D-Druck Kostenkalkulator

- Single-Page HTML-App mit allen 18 Eingabefeldern
- 12 Berechnungen live (calc.js, reine Funktionen)
- LocalStorage-Persistenz, Mehrfach-Projekte via Sidebar
- Excel Im-/Export ueber SheetJS (vendored, MIT)
- Drag&Drop + File-Picker-Import
- Apple-Swiss-Styling, responsive
- Vorlagen-Excel mit 3 Reitern (Eingabe/Kalkulation/Angebot), Formeln referenzieren Eingabe
- openpyxl-Script fuer reproduzierbaren Template-Build
- 5 Test-Szenarien validiert

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

assets/calc.js

@@ -0,0 +1,68 @@
+/* Berechnungslogik — 12 Formeln laut Spec */
+/* global window */
+
+/**
+ * @typedef {Object} Inputs
+ * @property {number} materialCostPerKg
+ * @property {number} materialUsageG
+ * @property {number} printTimeH
+ * @property {number} machineRate
+ * @property {number} powerKwh
+ * @property {number} powerPrice
+ * @property {number} postMin
+ * @property {number} postRate
+ * @property {number} packagingCost
+ * @property {number} shippingCost
+ * @property {number} setupCost
+ * @property {number} scrapPct
+ * @property {number} marginPct
+ * @property {number} quantity
+ * @property {number} individualAdjustment
+ * @property {number} vatPct
+ */
+
+const num = (v) => {
+  const n = parseFloat(v);
+  return Number.isFinite(n) ? n : 0;
+};
+
+const round2 = (v) => Math.round(v * 100) / 100;
+
+/**
+ * Alle 12 Berechnungen.
+ * @param {Object} s State-Objekt
+ * @returns {Object} Ergebnisse
+ */
+const calculate = (s) => {
+  const materialCost = num(s.materialUsageG) * (num(s.materialCostPerKg) / 1000);
+  const machineCost = num(s.printTimeH) * num(s.machineRate);
+  const energyCost = num(s.printTimeH) * num(s.powerKwh) * num(s.powerPrice);
+  const postCost = (num(s.postMin) / 60) * num(s.postRate);
+  const totalProduction = materialCost + machineCost + energyCost + postCost
+    + num(s.setupCost) + num(s.packagingCost) + num(s.shippingCost);
+  const scrapSurcharge = totalProduction * (num(s.scrapPct) / 100);
+  const subtotalNet = totalProduction + scrapSurcharge;
+  const margin = subtotalNet * (num(s.marginPct) / 100);
+  const customerNet = subtotalNet + margin + num(s.individualAdjustment);
+  const qty = Math.max(1, num(s.quantity) || 1);
+  const unitNet = customerNet / qty;
+  const unitGross = unitNet * (1 + num(s.vatPct) / 100);
+  const totalGross = unitGross * qty;
+
+  return {
+    materialCost: round2(materialCost),
+    machineCost: round2(machineCost),
+    energyCost: round2(energyCost),
+    postCost: round2(postCost),
+    totalProduction: round2(totalProduction),
+    scrapSurcharge: round2(scrapSurcharge),
+    subtotalNet: round2(subtotalNet),
+    margin: round2(margin),
+    customerNet: round2(customerNet),
+    unitNet: round2(unitNet),
+    unitGross: round2(unitGross),
+    totalGross: round2(totalGross),
+  };
+};
+
+window.Calc = { calculate, round2, num };