Add missing macros.fpp include for ASSERT macro in m_start_up.fpp

The @:ASSERT call added in d614938 requires the macros.fpp include,
which was missing, causing Fypp preprocessing to fail in the
documentation build.

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

Author: sbryngelson

src/pre_process/m_start_up.fpp

@@ -2,6 +2,8 @@
 !! @file
 !! @brief Contains module m_start_up
 
+#:include 'macros.fpp'
+
 !> @brief Reads and validates user inputs, loads existing grid/IC data, and initializes pre-process modules
 module m_start_up