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/revoke_token.rs

@@ -0,0 +1,12 @@
+use domain::{
+    errors::DomainError,
+    value_objects::{UserId, WebhookTokenId},
+};
+
+use crate::{context::AppContext, integrations::commands::RevokeWebhookTokenCommand};
+
+pub async fn execute(ctx: &AppContext, cmd: RevokeWebhookTokenCommand) -> Result<(), DomainError> {
+    let user_id = UserId::from_uuid(cmd.user_id);
+    let token_id = WebhookTokenId::from_uuid(cmd.token_id);
+    ctx.repos.webhook_token.delete(&token_id, &user_id).await
+}