The Texas Senate on Monday gave final approval to a $308 billion spending plan for the next two years, sending budget leaders into high-stakes negotiations with their counterparts in the House over property taxes and other divisive issues — with just weeks to go before the legislative session ends. Senators voted 31-0 to spend $141.2 billion in general revenue on major investments in property tax cuts, juvenile justice, mental health, higher education, state parks, historical sites and pay raises for teachers and state employees. State Rep. Joan Huffman, R-Houston, chair of the Senate Finance Committee, which oversaw the budget-writing process for the chamber, said “smart fiscal policy” over the last several sessions allowed budget writers to make historic investments thanks to an unprecedented surplus in state coffers.