LR-EXP-PHOTOS: Apple Photos fixes from the live test and review

- Ten minutes plus five seconds a file per import (was one minute): the
  first live run timed out while macOS's permission prompt was still up,
  and Photos' duplicates question waits for a person too.
- Files go to osascript 200 at a time, all within the import's one time
  limit: one run with every path went over macOS's 1 MiB argument limit
  at about 10,000 files, and Photos got nothing. A failed later batch says
  how many files Photos had added.
- The progress line "Adding to Apple Photos…" is translated on the UI
  thread; on the export worker it was always English.
- docs/apple-photos.md: who can add what (the control port is reachable by
  any local program, other users' included), batching, the new limit, and
  tested end to end (macOS 26.6.2, Photos 11.0, packaged app). The parity
  row says so; What's New has an entry.

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

crates/ui-egui/src/export_task.rs

@@ -48,6 +48,8 @@ pub fn start(app: &mut LightcraftApp, items: Vec<PreparedExport>, opts: ExportOp
     let cancel = Arc::new(AtomicBool::new(false));
     let (tx, rx) = channel();
     let (p, c) = (progress.clone(), cancel.clone());
+    // translated here: the language is the UI thread's, and the worker would show English
+    let adding = crate::i18n::tr("Adding to Apple Photos…").to_string();
     let work = move || {
         let mut w = |path: &str, bytes: &[u8]| write(path, bytes);
         let r = run_batch(items, &opts, &to, &mut w, &|path| std::path::Path::new(path).exists(), false, &mut |done, name| {
@@ -60,7 +62,7 @@ pub fn start(app: &mut LightcraftApp, items: Vec<PreparedExport>, opts: ExportOp
             if !after.is_none()
                 && let Ok(mut g) = p.lock()
             {
-                g.1 = crate::i18n::tr("Adding to Apple Photos…").to_string();
+                g.1 = adding;
             }
             let photos = after.run(&files, c.load(Ordering::Relaxed));
             (files, photos)