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/get_diary.rs

@@ -0,0 +1,29 @@
+use domain::{
+    errors::DomainError,
+    models::{
+        DiaryEntry, DiaryFilter, SortDirection,
+        collections::{PageParams, Paginated},
+    },
+    value_objects::{MovieId, UserId},
+};
+
+use crate::{context::AppContext, diary::queries::GetDiaryQuery};
+
+pub async fn execute(
+    ctx: &AppContext,
+    query: GetDiaryQuery,
+) -> Result<Paginated<DiaryEntry>, DomainError> {
+    let page = PageParams::new(query.limit, query.offset)?;
+    let movie_id = query.movie_id.map(MovieId::from_uuid);
+    let user_id = query.user_id.map(UserId::from_uuid);
+
+    let filter = DiaryFilter {
+        sort_by: query.sort_by.unwrap_or(SortDirection::Descending),
+        page,
+        movie_id,
+        user_id,
+        search: None,
+    };
+
+    ctx.repos.diary.query_diary(&filter).await
+}