[Emacs] Add function to reschedule past items to today

Adds imalison:reschedule-past-to-today which iterates through agenda
files and reschedules any incomplete TODO items with a SCHEDULED date
in the past to the current date.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

nixos/synergy-cstdint.patch

@@ -0,0 +1,12 @@
+diff --git a/src/lib/server/InputFilter.cpp b/src/lib/server/InputFilter.cpp
+index 1234567..abcdefg 100644
+--- a/src/lib/server/InputFilter.cpp
++++ b/src/lib/server/InputFilter.cpp
+@@ -26,6 +26,7 @@
+ #include <cstdlib>
+ #include <sstream>
+ #include <cstring>
++#include <cstdint>
+
+ // -----------------------------------------------------------------------------
+ // Input Filter Condition