feat: implement category flags, drop global tables, fix sidebar sticky layout

shop/lib/actions/validation.ts

@@ -7,6 +7,8 @@ export function validateWizardSelections(
 ): void {
   for (const cat of dbCategories) {
     const sel = selections[cat.id]
+
+    // --- is_required: Pflichtauswahl prüfen ---
     const hasSelection = sel && (
       (cat.allow_multiselect && sel.productIds && sel.productIds.length > 0) ||
       (!cat.allow_multiselect && sel.productId)
@@ -17,6 +19,13 @@ export function validateWizardSelections(
     }
 
     if (sel) {
+      // --- allow_multiselect = false: keine doppelten IDs erlaubt ---
+      if (!cat.allow_multiselect && sel.productIds && sel.productIds.length > 1) {
+        throw new Error(
+          `Die Kategorie "${cat.name}" erlaubt keine Mehrfachauswahl. Bitte nur ein Produkt wählen.`
+        )
+      }
+
       const selectedProds: Product[] = []
       if (cat.allow_multiselect && sel.productIds) {
         sel.productIds.forEach(pId => {
@@ -32,8 +41,8 @@ export function validateWizardSelections(
         // Validate selected modules
         for (const mId of sel.moduleIds) {
           const mod = prod.modules?.find(m => m.id === mId)
-          if (!mod) continue // module might belong to another selected product in the same category, so skip error if it's not this one's
-          
+          if (!mod) continue
+
           // Requirements check
           if (mod.requirements && mod.requirements.length > 0) {
             const hasMetRequirement = mod.requirements.some(reqId => sel.moduleIds.includes(reqId))
@@ -53,7 +62,7 @@ export function validateWizardSelections(
     }
   }
 
-  // Product-level constraints validation
+  // --- Product-level constraints validation ---
   const selectedProductIds: string[] = []
   Object.values(selections).forEach(s => {
     if (s.productIds && s.productIds.length > 0) {
@@ -92,3 +101,4 @@ export function validateWizardSelections(
     }
   }
 }
+