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/commands.rs

@@ -0,0 +1,34 @@
+use uuid::Uuid;
+
+pub struct IngestWatchEventCommand {
+    pub token: String,
+    pub raw_payload: Vec<u8>,
+    pub source: domain::models::WatchEventSource,
+}
+
+pub struct WatchEventConfirmation {
+    pub watch_event_id: Uuid,
+    pub rating: u8,
+    pub comment: Option<String>,
+}
+
+pub struct ConfirmWatchEventsCommand {
+    pub user_id: Uuid,
+    pub confirmations: Vec<WatchEventConfirmation>,
+}
+
+pub struct DismissWatchEventsCommand {
+    pub user_id: Uuid,
+    pub event_ids: Vec<Uuid>,
+}
+
+pub struct GenerateWebhookTokenCommand {
+    pub user_id: Uuid,
+    pub provider: domain::models::WatchEventSource,
+    pub label: Option<String>,
+}
+
+pub struct RevokeWebhookTokenCommand {
+    pub user_id: Uuid,
+    pub token_id: Uuid,
+}