Add Spoiler Flag with veil, AP content-warning encoding, and full-stack plumbing

Authors can flag a review's comment as containing spoilers; the comment is
blurred behind a reveal control for every viewer except the author, omitted
from RSS, and federates as containsSpoilers plus an AP summary content
warning (ADR-0011) so Mastodon-class clients also collapse it. Flag follows
the general-edit path (ADR-0001) across domain, both DB backends, REST,
HTML templates, SPA (shadcn), TUI fixtures, and exports.

crates/domain/src/models/tests/review.rs

@@ -12,6 +12,7 @@ fn make_review(watch_medium: Option<WatchMedium>) -> Review {
         Some(Comment::new("great film".into()).unwrap()),
         NaiveDateTime::parse_from_str("2024-06-15 20:00:00", "%Y-%m-%d %H:%M:%S").unwrap(),
         watch_medium,
+        false,
     )
     .unwrap()
 }
@@ -71,6 +72,23 @@ fn apply_edit_clears_watch_medium() {
     assert_eq!(edited.watch_medium(), None);
 }
 
+#[test]
+fn apply_edit_toggles_spoilers() {
+    let original = make_review(None);
+    let flag_on = original.apply_edit(ReviewEdit {
+        spoilers: Some(true),
+        ..Default::default()
+    });
+    assert!(flag_on.spoilers());
+    let flag_off = flag_on.apply_edit(ReviewEdit {
+        spoilers: Some(false),
+        ..Default::default()
+    });
+    assert!(!flag_off.spoilers());
+    let untouched = original.apply_edit(ReviewEdit::default());
+    assert!(!untouched.spoilers());
+}
+
 #[test]
 fn apply_edit_no_changes_preserves_all() {
     let original = make_review(Some(WatchMedium::TV));