feat: complete session — catalog, marketplace, WhatsApp, peer-to-peer, install scripts

Major features:
- Pixel-Perfect glassmorphism design (landing + POS + public catalog)
- OEM/Local catalog toggle with Nexpart taxonomy (14 groups, 108 subgroups, 558 part types)
- Marketplace B2B Phase 1 (bodegas, POs, status machine, WA+email notifications)
- Peer-to-peer inventory (multi-instance, LAN discovery)
- WhatsApp: photo→Vision AI, voice→Whisper, conversational quotations
- Smart unified search (VIN/plate/part_number/keyword auto-detect)
- Shop Supplies tab (vehicle-independent parts)
- Chatbot AI fallback chain (5 models) + response cache
- CSV inventory import tool + setup_instance.sh installer
- Tablet-responsive CSS + sidebar toggle
- Filters, export CSV, employee edit, business data save
- Quotation system (WA→POS) with auto-print on confirmation
- Live stats on landing page

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pos/static/js/accounting.js

@@ -390,7 +390,37 @@ const Accounting = (() => {
 
     // ---- Exportar placeholder ----
     function exportarContabilidad() {
-        alert('Exportar: proximamente');
+        // Find the first visible table in the active accounting tab and export as CSV
+        var tables = document.querySelectorAll('table');
+        var table = null;
+        for (var i = 0; i < tables.length; i++) {
+            if (tables[i].offsetParent !== null && tables[i].querySelector('tbody tr')) {
+                table = tables[i];
+                break;
+            }
+        }
+        if (!table) {
+            alert('No hay datos para exportar en la vista actual.');
+            return;
+        }
+        var rows = [];
+        var ths = table.querySelectorAll('thead th');
+        if (ths.length) {
+            rows.push(Array.from(ths).map(function(th) { return '"' + th.textContent.trim().replace(/"/g, '""') + '"'; }).join(','));
+        }
+        table.querySelectorAll('tbody tr').forEach(function(tr) {
+            var cells = tr.querySelectorAll('td');
+            rows.push(Array.from(cells).map(function(td) { return '"' + td.textContent.trim().replace(/"/g, '""') + '"'; }).join(','));
+        });
+        if (rows.length <= 1) { alert('Sin datos para exportar.'); return; }
+        var csv = rows.join('\n');
+        var blob = new Blob(['\uFEFF' + csv], { type: 'text/csv;charset=utf-8;' });
+        var url = URL.createObjectURL(blob);
+        var a = document.createElement('a');
+        a.href = url;
+        a.download = 'contabilidad_nexus_' + new Date().toISOString().slice(0, 10) + '.csv';
+        a.click();
+        URL.revokeObjectURL(url);
     }
 
     // ---- Nueva Poliza modal ----