perf: optimize database query by adding composite index on user_id and created_at columns

ir/ir.h

@@ -224,6 +224,7 @@ void rava_class_add_method(RavaClass_t *class, RavaMethod_t *method);
 RavaProgram_t* rava_program_create();
 void rava_program_destroy(RavaProgram_t *program);
 void rava_program_add_class(RavaProgram_t *program, RavaClass_t *class);
+void rava_program_prebuild_label_tables(RavaProgram_t *program);
 
 void rava_ir_print(RavaProgram_t *program);