Fix ox-hugo export with internal ID links and Quartz config

- Add org-id resolution for [[id:...]] links by building ID locations
  database once before parallel export
- Handle broken file links gracefully with org-export-with-broken-links
- Fix race condition in parallel exports by pre-building ID cache
- Fix Quartz config not being applied: cp was preserving nix store hash
  prefix in filename instead of using explicit destination filename
- Continue pipeline even when some exports fail, reporting failures
- Improve error handling and logging throughout export pipeline

lib/org_garden/telemetry.ex

@@ -74,7 +74,7 @@ defmodule OrgGarden.Telemetry do
   end
 
   defp handle_event([:org_garden, :export, :exception], _measurements, metadata, _config) do
-    Logger.error("Export failed: #{metadata.file} - #{inspect(metadata.reason)}")
+    Logger.error("Export failed: #{metadata.file}")
   end
 
   defp handle_event([:org_garden, :watcher, :file_processed], _measurements, metadata, _config) do