fix: show all marketplaces (incl. Amazon UK) in experiment form

Use a hardcoded ALL_MARKETPLACES list instead of deriving from current
filtered data, so Amazon UK is always available even when viewing PAN-EU.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

components/ExperimentTracker.tsx

@@ -61,6 +61,8 @@ const STATUS_LABELS: Record<ExperimentStatus, string> = {
     'failed': 'Failed',
 };
 
+const ALL_MARKETPLACES = ['Amazon DE', 'Amazon IT', 'Amazon FR', 'Amazon ES', 'Amazon UK'];
+
 const STORAGE_KEY = 'craze_experiments';
 
 // --- Storage helpers ---
@@ -179,18 +181,12 @@ const ExperimentTracker: React.FC<ExperimentTrackerProps> = ({ rows, weeks, prim
     const [formDesc, setFormDesc] = useState('');
     const [formImpact, setFormImpact] = useState<ExpectedImpact>('More Sales');
 
-    // Available marketplaces from data
-    const marketplaces = useMemo(() => {
-        const mks = new Set(rows.map(r => r.customer).filter(Boolean));
-        return Array.from(mks).sort();
-    }, [rows]);
-
     // Default marketplace to active filter when opening form
     const defaultMarketplace = useMemo(() => {
         if (customerFilters.length === 1) return customerFilters[0];
         if (customerFilters.length > 0) return customerFilters[0];
-        return marketplaces[0] || '';
-    }, [customerFilters, marketplaces]);
+        return ALL_MARKETPLACES[0];
+    }, [customerFilters]);
 
     // Available product lines from data
     const productLines = useMemo(() => {
@@ -445,7 +441,7 @@ const ExperimentTracker: React.FC<ExperimentTrackerProps> = ({ rows, weeks, prim
                                     className="w-full bg-slate-950 border border-white/10 rounded-lg px-3 py-2 text-sm text-white focus:outline-none focus:ring-2 focus:ring-indigo-500"
                                 >
                                     <option value="">Select marketplace...</option>
-                                    {marketplaces.map(mk => (
+                                    {ALL_MARKETPLACES.map(mk => (
                                         <option key={mk} value={mk}>{mk}</option>
                                     ))}
                                 </select>