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/import/list_profiles.rs

@@ -0,0 +1,9 @@
+use crate::context::AppContext;
+use domain::{errors::DomainError, models::ImportProfile, value_objects::UserId};
+
+pub async fn execute(
+    ctx: &AppContext,
+    user_id: &UserId,
+) -> Result<Vec<ImportProfile>, DomainError> {
+    ctx.repos.import_profile.list_for_user(user_id).await
+}