fix: ventas page only shows CMXC records, remove duplicate column

- _query_rows now always filters by PREFIJO='CMXC' (unless user specifies another prefix in the factura field)
- Removed redundant first column IDRECEP from ventas table (factura_key and factura were identical)
- Renamed header to just Factura

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

app/templates/ventas.html

@@ -175,7 +175,6 @@ function renderTabla() {
     let html = `<div class="overflow-x-auto">
     <table class="w-full text-xs">
         <thead><tr class="text-left text-gray-400 border-b border-gray-200">
-            <th class="pb-2 font-medium pr-3">IDRECEP.</th>
             <th class="pb-2 font-medium pr-3">Factura</th>
             <th class="pb-2 font-medium pr-3">Paciente</th>
             <th class="pb-2 font-medium pr-3">Contrato</th>
@@ -220,7 +219,6 @@ function filaHtml(item) {
 
     return `<tr id="${rowId}" class="border-b border-gray-50 hover:bg-gray-50/80 transition-colors ${rowCls}">
         <td class="py-2 pr-3 font-mono text-gray-600">${escHtml(id)}</td>
-        <td class="py-2 pr-3 text-gray-600">${escHtml(String(item.factura || '-'))}</td>
         <td class="py-2 pr-3 text-gray-600">${escHtml(String(item.paciente || '-'))}</td>
         <td class="py-2 pr-3"><span class="px-1.5 py-0.5 bg-emerald-100 text-emerald-700 rounded text-xs font-mono">${escHtml(String(item.contrato || '-'))}</span></td>
         <td class="py-2 pr-3 text-gray-500 max-w-[180px] truncate" title="${escAttr(examsStr)}">${escHtml(examsStr)}</td>