test: move application tests to tests/

test_support/test_helpers -> tests/support; watched_at unified w/ domain test_watched_at (2024-03-15).
Kept inline: users::diary_filter tests (feed_sort_to_direction_all_variants, paged_user_filter_builds_correctly) - pub(super) helpers in private module.
Dropped stale never-compiled users/tests/get_users.rs (old execute signature).

crates/application/tests/diary/get_diary_test.rs

@@ -0,0 +1,26 @@
+use domain::testing::FakeDiaryQuery;
+use std::sync::Arc;
+
+use application::{diary::deps::GetDiaryDeps, diary::get_diary, diary::queries::GetDiaryQuery};
+
+#[tokio::test]
+async fn returns_empty_page() {
+    let diary = FakeDiaryQuery::new() as Arc<dyn domain::ports::DiaryQuery>;
+    let deps = GetDiaryDeps { diary };
+
+    let result = get_diary::execute(
+        &deps,
+        GetDiaryQuery {
+            limit: None,
+            offset: None,
+            sort_by: None,
+            movie_id: None,
+            user_id: None,
+        },
+    )
+    .await
+    .unwrap();
+
+    assert!(result.items.is_empty());
+    assert_eq!(result.total_count, 0);
+}