application: channels bounded context

CQRS use cases (create/update/delete/get/list/list_by_owner),
ownership checks, auto-snapshot on config change.
Channel setters added to domain model.

crates/application/src/channels/update.rs

@@ -0,0 +1,68 @@
+use domain::events::DomainEvent;
+use domain::models::Channel;
+use domain::value_objects::{ChannelId, UserId};
+use domain::{DomainError, DomainResult};
+
+use super::commands::UpdateChannelCommand;
+use super::deps::ChannelCommandDeps;
+
+/// Update an existing channel.
+///
+/// Flow: find channel -> verify ownership -> snapshot config if changed ->
+/// apply updates -> save -> publish event -> return.
+pub async fn execute(deps: &ChannelCommandDeps, cmd: UpdateChannelCommand) -> DomainResult<Channel> {
+    let channel_id = ChannelId::from(cmd.channel_id);
+    let owner_id = UserId::from(cmd.owner_id);
+
+    let mut channel = deps
+        .channel_query
+        .find_by_id(channel_id)
+        .await?
+        .ok_or(DomainError::ChannelNotFound(cmd.channel_id))?;
+
+    // Ownership check
+    if channel.owner_id() != owner_id {
+        return Err(DomainError::forbidden("You don't own this channel"));
+    }
+
+    // Auto-snapshot the current config before overwriting
+    if cmd.schedule_config.is_some() {
+        deps.channel_command
+            .save_config_snapshot(channel_id, channel.schedule_config(), None)
+            .await?;
+    }
+
+    // Apply partial updates
+    if let Some(name) = cmd.name {
+        channel.set_name(name);
+    }
+    if let Some(description) = cmd.description {
+        channel.set_description(description);
+    }
+    if let Some(timezone) = cmd.timezone {
+        channel.set_timezone(timezone);
+    }
+    if let Some(config) = cmd.schedule_config {
+        channel.set_schedule_config(config);
+    }
+    if let Some(policy) = cmd.recycle_policy {
+        channel.set_recycle_policy(policy);
+    }
+    if let Some(auto) = cmd.auto_schedule {
+        channel.set_auto_schedule(auto);
+    }
+
+    deps.channel_command.save(&channel).await?;
+
+    deps.event_publisher
+        .publish(DomainEvent::ChannelUpdated {
+            channel_id: channel.id(),
+        })
+        .await?;
+
+    Ok(channel)
+}
+
+#[cfg(test)]
+#[path = "tests/update.rs"]
+mod tests;