Quests: main quest items no longer refused, restart resets bit-field variables

AddMainQuestItem refused every new main quest item once the list held an
entry with script id 0 (scripts give such items); the Goldbeeren of quest
402 were picked up and lost. The script id test is patched out.

Quest variables are bit fields (op 0x44 sets a bit): the quest giver
restart now writes the values directly, 0 and 1 (available) for the
variable named after the quest.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CMakeLists.txt

@@ -82,6 +82,7 @@ add_library(sacredK SHARED
     src/mods/followers.cpp
     src/mods/questfail.cpp
     src/mods/questgiver.cpp
+    src/mods/questitems.cpp
     src/mods/questnpc.cpp
     src/mods/anticheat.cpp
     src/mods/loadingscreen.cpp