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/application/src/diary/commands.rs

@@ -17,6 +17,7 @@ pub struct LogReviewCommand {
     pub comment: Option<String>,
     pub watched_at: NaiveDateTime,
     pub watch_medium: Option<WatchMedium>,
+    pub spoilers: bool,
 }
 
 pub struct DeleteReviewCommand {
@@ -31,6 +32,7 @@ pub struct EditReviewCommand {
     pub comment: Option<Option<String>>,
     pub watched_at: Option<NaiveDateTime>,
     pub watch_medium: Option<Option<WatchMedium>>,
+    pub spoilers: Option<bool>,
 }
 
 #[derive(Clone)]