add 400+ unit tests for domain and application layers

Extract ReviewLogger trait to decouple import/integrations
from diary::log_review (cross-module coupling smell).

Add in-memory fakes for all repository ports, enabling
isolated testing of every use case module without a database.

Coverage: domain+application 22% → 80%, 427 tests.

crates/application/src/integrations/revoke_token.rs

@@ -10,3 +10,7 @@ pub async fn execute(ctx: &AppContext, cmd: RevokeWebhookTokenCommand) -> Result
     let token_id = WebhookTokenId::from_uuid(cmd.token_id);
     ctx.repos.webhook_token.delete(&token_id, &user_id).await
 }
+
+#[cfg(test)]
+#[path = "tests/revoke_token.rs"]
+mod tests;