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/integrations/dismiss.rs

@@ -0,0 +1,35 @@
+use domain::{
+    errors::DomainError,
+    models::WatchEventStatus,
+    value_objects::{UserId, WatchEventId},
+};
+
+use crate::{context::AppContext, integrations::commands::DismissWatchEventsCommand};
+
+pub async fn execute(ctx: &AppContext, cmd: DismissWatchEventsCommand) -> Result<u32, DomainError> {
+    let user_id = UserId::from_uuid(cmd.user_id);
+    let mut dismissed = 0u32;
+
+    for id in cmd.event_ids {
+        let event_id = WatchEventId::from_uuid(id);
+        let event = ctx
+            .repos
+            .watch_event
+            .get_by_id(&event_id)
+            .await?
+            .ok_or_else(|| DomainError::NotFound(format!("WatchEvent {id}")))?;
+
+        if event.user_id() != &user_id {
+            return Err(DomainError::Unauthorized("not your watch event".into()));
+        }
+
+        ctx.repos
+            .watch_event
+            .update_status(&event_id, WatchEventStatus::Dismissed)
+            .await?;
+
+        dismissed += 1;
+    }
+
+    Ok(dismissed)
+}