refactor: group use cases into DDD bounded contexts

Flat use_cases/ (44 files) + monolithic commands.rs/queries.rs
split into diary/, movies/, watchlist/, import/, auth/, users/,
integrations/, search/, person/, federation/ — each with own
commands.rs, queries.rs, and use case modules.

Inline tests extracted to sibling tests/ dirs.

crates/application/src/diary/delete_review.rs

@@ -0,0 +1,61 @@
+use crate::{context::AppContext, diary::commands::DeleteReviewCommand};
+use domain::{
+    errors::DomainError,
+    events::DomainEvent,
+    value_objects::{ReviewId, UserId},
+};
+
+pub async fn execute(ctx: &AppContext, cmd: DeleteReviewCommand) -> Result<(), DomainError> {
+    let review_id = ReviewId::from_uuid(cmd.review_id);
+    let requesting_user_id = UserId::from_uuid(cmd.requesting_user_id);
+
+    let review = ctx
+        .repos
+        .review
+        .get_review_by_id(&review_id)
+        .await?
+        .ok_or_else(|| DomainError::NotFound(format!("review {}", cmd.review_id)))?;
+
+    if review.user_id() != &requesting_user_id {
+        return Err(DomainError::Unauthorized("not your review".into()));
+    }
+
+    let movie_id = review.movie_id().clone();
+    ctx.repos.review.delete_review(&review_id).await?;
+
+    if let Err(e) = ctx
+        .services
+        .event_publisher
+        .publish(&DomainEvent::ReviewDeleted {
+            review_id: review_id.clone(),
+            user_id: requesting_user_id.clone(),
+        })
+        .await
+    {
+        tracing::warn!("failed to publish ReviewDeleted: {e}");
+    }
+
+    let history = ctx.repos.diary.get_review_history(&movie_id).await?;
+    if history.viewings().is_empty() {
+        let poster_path = history.movie().poster_path().cloned();
+        ctx.repos.movie.delete_movie(&movie_id).await?;
+        // best-effort: movie is already deleted, so publish failure is non-fatal
+        if let Err(e) = ctx
+            .services
+            .event_publisher
+            .publish(&DomainEvent::MovieDeleted {
+                movie_id,
+                poster_path,
+            })
+            .await
+        {
+            tracing::warn!("failed to publish MovieDeleted event: {e}");
+        }
+    }
+
+    Ok(())
+}
+
+#[cfg(test)]
+#[path = "tests/delete_review.rs"]
+mod tests;