portfolio-edit: add button writes position to localStorage

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/static/js/portfolio_edit.js

@@ -124,4 +124,56 @@
   tickerInput.addEventListener('blur', validateTicker);
   document.getElementById('pf-add-qty').addEventListener('input', updateSubmitState);
   document.getElementById('pf-add-cost').addEventListener('input', updateSubmitState);
+
+  // ---- Add button → localStorage merge -------------------------------
+
+  function resetForm() {
+    tickerInput.value = '';
+    document.getElementById('pf-add-qty').value = '';
+    document.getElementById('pf-add-cost').value = '';
+    document.getElementById('pf-add-date').value = '';
+    validated = null;
+    setStatus(tickerStatus, '', '');
+    costCurrencyEl.textContent = '';
+    clearDuplicateWarning();
+    updateSubmitState();
+    tickerInput.focus();
+  }
+
+  function addPosition() {
+    if (submitBtn.disabled) return;
+    const qty  = parseFloat(document.getElementById('pf-add-qty').value);
+    const cost = parseFloat(document.getElementById('pf-add-cost').value);
+    const sym  = validated.symbol;
+
+    const pie = window.CassandraPortfolio.loadPie() || {
+      pie_name: null,
+      base_currency: 'GBP',
+      positions: [],
+      totals: {invested: 0, value: 0, result: 0},
+      warnings: [],
+    };
+    pie.positions = pie.positions || [];
+    pie.positions.push({
+      yahoo_ticker: sym,
+      t212_slice:   sym,                // shared shape with CSV path
+      name:         validated.name || sym,
+      qty:          qty,
+      avg_cost:     cost,
+      currency:     validated.currency || 'USD',
+    });
+    window.CassandraPortfolio.savePie(pie);
+    window.CassandraPortfolio.mountAndRender();
+    resetForm();
+  }
+
+  submitBtn.addEventListener('click', addPosition);
+
+  // Submit on Enter from any input within the form.
+  form.addEventListener('keydown', function (e) {
+    if (e.key === 'Enter' && !submitBtn.disabled) {
+      e.preventDefault();
+      addPosition();
+    }
+  });
 })();