feat(pos/workshop): add 80mm thermal ticket printing for service orders

- Add generate_service_order_ticket() in thermal_printer.py with ESC/POS commands for 58mm and 80mm printers.

- Add POST /pos/api/service-orders/:id/print endpoint returning raw bytes or JSON for browser rendering.

- Extend printer.js with printServiceOrder() using WebUSB/Web Serial.

- Add Imprimir orden button in workshop.js detail modal.

- Update FASES_IMPLEMENTADAS.md.

pos/blueprints/service_order_bp.py

@@ -369,3 +369,61 @@ def delete_catalog_item(item_id):
         return jsonify({'message': 'Catalog item deactivated'})
     finally:
         conn.close()
+
+
+# ─── Thermal printing ─────────────────────────────
+
+
+@service_order_bp.route('/<int:so_id>/print', methods=['POST'])
+@require_auth()
+def print_service_order_ticket(so_id):
+    """Generate a printable ticket for a service order.
+
+    Body (optional): {printer_type: 'escpos_raw' | 'browser', width: 58 | 80}
+      - escpos_raw: returns raw ESC/POS bytes (application/octet-stream)
+      - browser: returns the data dict as JSON for browser-side rendering
+    """
+    from flask import Response
+    from services.thermal_printer import generate_service_order_ticket
+
+    body = request.get_json(silent=True) or {}
+    printer_type = body.get('printer_type', 'escpos_raw')
+    width = int(body.get('width', 80))
+
+    conn = get_tenant_conn(g.tenant_id)
+    cur = conn.cursor()
+
+    order = get_service_order(conn, so_id)
+    if not order:
+        cur.close()
+        conn.close()
+        return jsonify({'error': 'Service order not found'}), 404
+
+    # Fetch business info from config
+    business_info = {'name': 'NEXUS AUTOPARTS', 'rfc': '', 'address': ''}
+    try:
+        cur.execute(
+            "SELECT key, value FROM config WHERE key IN ('business_name','rfc','address')"
+        )
+        for rw in cur.fetchall():
+            if rw[0] == 'business_name':
+                business_info['name'] = rw[1]
+            else:
+                business_info[rw[0]] = rw[1]
+    except Exception:
+        pass
+
+    cur.close()
+    conn.close()
+
+    if printer_type == 'browser':
+        return jsonify(order)
+
+    raw = generate_service_order_ticket(order, business_info, width=width)
+    return Response(
+        raw,
+        mimetype='application/octet-stream',
+        headers={
+            'Content-Disposition': f'attachment; filename=orden_{order.get("order_number", so_id)}.bin'
+        },
+    )