Implement dynamic currency display based on portfolio majority

- Add getMajorityCurrency() to calculate which currency holds most value
- Include both ETF positions and cash accounts in currency calculation
- Update formatCurrency() to use majority currency symbol by default
- Dashboard now displays in EUR/USD/GBP based on portfolio composition
- Automatic currency switching improves user experience and accuracy
- Maintain backward compatibility with optional currency parameter

🤖 Generated with [Claude Code](https://claude.ai/code)

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

script.js

@@ -1418,14 +1418,18 @@ class ETFTradeTracker {
         breakdownList.innerHTML = breakdownHTML;
     }
 
-    formatCurrency(amount) {
+    formatCurrency(amount, currency = null) {
+        // Use majority currency if none specified
+        const currencyToUse = currency || this.getMajorityCurrency();
+        const symbol = this.getCurrencySymbol(currencyToUse);
+        
         const absAmount = Math.abs(amount);
         if (absAmount >= 1000000) {
-            return (amount >= 0 ? '€' : '-€') + (absAmount / 1000000).toFixed(2) + 'M';
+            return (amount >= 0 ? symbol : '-' + symbol) + (absAmount / 1000000).toFixed(2) + 'M';
         } else if (absAmount >= 1000) {
-            return (amount >= 0 ? '€' : '-€') + (absAmount / 1000).toFixed(1) + 'K';
+            return (amount >= 0 ? symbol : '-' + symbol) + (absAmount / 1000).toFixed(1) + 'K';
         } else {
-            return (amount >= 0 ? '€' : '-€') + absAmount.toFixed(2);
+            return (amount >= 0 ? symbol : '-' + symbol) + absAmount.toFixed(2);
         }
     }
 
@@ -2865,6 +2869,44 @@ class ETFTradeTracker {
         }
     }
 
+    getMajorityCurrency() {
+        const currencyValues = {
+            EUR: 0,
+            USD: 0,
+            GBP: 0
+        };
+
+        // Calculate total value by currency from ETF positions
+        const etfMap = this.getActiveETFPositions();
+        etfMap.forEach((etf, symbol) => {
+            const currentPrice = this.currentPrices.get(symbol);
+            const value = currentPrice ? etf.shares * currentPrice : etf.totalValue;
+            currencyValues[etf.currency] = (currencyValues[etf.currency] || 0) + value;
+        });
+
+        // Add cash accounts to the calculation
+        if (this.cashSummary && this.cashSummary.accounts) {
+            this.cashSummary.accounts.forEach(account => {
+                if (account.is_active && account.balance > 0) {
+                    currencyValues[account.currency] = (currencyValues[account.currency] || 0) + parseFloat(account.balance);
+                }
+            });
+        }
+
+        // Find the currency with the highest value
+        let majorityCurrency = 'EUR'; // default
+        let maxValue = 0;
+        
+        for (const [currency, value] of Object.entries(currencyValues)) {
+            if (value > maxValue) {
+                maxValue = value;
+                majorityCurrency = currency;
+            }
+        }
+
+        return majorityCurrency;
+    }
+
     escapeHtml(text) {
         const div = document.createElement('div');
         div.textContent = text;