back button and null selection

static/js/api.js

@@ -92,10 +92,14 @@ window.sendCommand = async function() {
   if (!town) return alert('Select a town first.');
 
   const type = document.getElementById('cmd-type').value;
+  if (!type) return alert('Παρακαλώ επιλέξτε Ενέργεια (Command Type) πρώτα.');
+
   let payload = {};
 
   if (type === 'build') {
     const building_id = document.getElementById('building-select').value;
+    if (!building_id) return alert('Παρακαλώ επιλέξτε Κατασκευή πρώτα.');
+    
     const bData = town.build_data?.[building_id];
     
     // UI Validation logic
@@ -123,6 +127,8 @@ window.sendCommand = async function() {
     payload = { building_id };
   } else if (type === 'recruit') {
     const unit_id = document.getElementById('unit-select').value;
+    if (!unit_id) return alert('Παρακαλώ επιλέξτε Μονάδα προς εκπαίδευση.');
+    
     const amount = parseInt(document.getElementById('recruit-amount').value) || 1;
     const uData = town.unit_data?.[unit_id];
     

static/js/components/commandForm.js

@@ -18,7 +18,7 @@ window.renderBuildingDropdown = function() {
   const bData   = town.build_data || {};
   
   const currentVal = bSelect.value;
-  bSelect.innerHTML = '';
+  bSelect.innerHTML = '<option value="" disabled selected>-- Επιλέξτε Κατασκευή --</option>';
   
   for (const [key, nameGr] of Object.entries(window.BUILDING_NAMES_GR)) {
     const level = bLevels[key] !== undefined ? bLevels[key] : "?";
@@ -82,7 +82,7 @@ window.renderUnitDropdown = function() {
   const uData   = town.unit_data || {};
   
   const currentVal = uSelect.value;
-  uSelect.innerHTML = '';
+  uSelect.innerHTML = '<option value="" disabled selected>-- Επιλέξτε Μονάδα --</option>';
 
   for (const [key, nameGr] of Object.entries(window.UNIT_NAMES_GR)) {
     if (key === 'militia') continue;