Fix marker crash on logout and add module lifecycle table

The marker cleanup hook on CleanupWorldAndEntities was never installed —
markers.installHooks() was missing from install() in main.zig. Entities
created via WorldMarker were never cleaned up before the game's atexit
handler iterated the hash table over freed heap memory.

Key changes:
- Add markers.installHooks() call (the actual crash fix)
- Replace manual install/uninstall/shutdown lists with a single modules
  table that drives all three phases — prevents this class of bug
- Gate marker Lua functions, addon, and keybindings behind isActive()
  so they're skipped when another DLL owns the hooks
- Add world_cleanup_hook.detach() to removeHooks() (was missing)
- Migrate from vendored libs/hook to external zhook dependency
- Unify installHooks return types to void across all modules
- Add diagnostic logging to marker cleanup (temporary, for testing)

src/markers/addon/Markers.lua

@@ -14,6 +14,13 @@ frame:SetScript("OnEvent", function()
     end
 end)
 
+-- Per-frame animation driver: queues Hold after Stand finishes on new
+-- markers and re-queues it periodically so it never falls back to Stand.
+local animFrame = CreateFrame("Frame")
+animFrame:SetScript("OnUpdate", function()
+    ProcessMarkerAnimations()
+end)
+
 SLASH_MARKERS1 = "/markers"
 SLASH_MARKERS2 = "/mark"
 SlashCmdList["MARKERS"] = function(msg)