feat(api): expand API endpoints for repo, PR, user, workspace management

- Add git operation endpoints: archive, compare branches, diff, tree,
  repository extras
- Add repo endpoints: contributors, delete fork, get branch/commit
  status/deploy key/invitation/member/release/tag/webhook, topics,
  release assets, webhook deliveries/retry
- Add PR endpoints: review requests, templates
- Add user endpoints: block/unblock, follow/unfollow, presence,
  personal access tokens, account restore
- Add workspace endpoints: billing history, approvals, domains,
  integrations, invitations, members, webhooks, restore
- Add internal API, notification API, IM API modules
- Update route configuration and OpenAPI spec

api/im/channel_get.rs

@@ -0,0 +1,52 @@
+use actix_web::{HttpResponse, web};
+use serde::Deserialize;
+use utoipa::IntoParams;
+
+use crate::api::response::{ApiErrorResponse, ApiResponse};
+use crate::error::AppError;
+use crate::models::base_info::resolve_users;
+use crate::models::channels::ChannelDetail;
+use crate::service::AppService;
+use crate::service::im::ImSession;
+use crate::session::Session;
+
+#[derive(Debug, Deserialize, IntoParams)]
+pub struct PathParams {
+    pub workspace_name: String,
+    pub channel_id: uuid::Uuid,
+}
+
+/// Get a channel
+#[utoipa::path(
+    get,
+    path = "/api/v1/im/workspaces/{workspace_name}/channels/{channel_id}",
+    tag = "IM",
+    operation_id = "imChannelGet",
+    params(PathParams),
+    responses(
+        (status = 200, description = "Channel retrieved successfully", body = ApiResponse<ChannelDetail>),
+        (status = 401, description = "Authentication required", body = ApiErrorResponse),
+        (status = 404, description = "Workspace or channel not found", body = ApiErrorResponse),
+        (status = 500, description = "Internal server error", body = ApiErrorResponse),
+    ),
+    security(("session_cookie" = []))
+)]
+pub async fn channel_get(
+    service: web::Data<AppService>,
+    session: Session,
+    path: web::Path<PathParams>,
+) -> Result<HttpResponse, AppError> {
+    let user_id = session.user().ok_or(AppError::Unauthorized)?;
+    let im_session = ImSession::new(user_id);
+    let channel = service
+        .im
+        .channel_get(&im_session, &path.workspace_name, path.channel_id)
+        .await?;
+
+    let db = &service.ctx.db;
+    let users = resolve_users(db, &[channel.created_by]).await?;
+    let creator = users.get(&channel.created_by).cloned().unwrap_or_default();
+    let detail = channel.into_detail(creator);
+
+    Ok(HttpResponse::Ok().json(ApiResponse::new(detail)))
+}