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/workspace/billing_history.rs

@@ -0,0 +1,39 @@
+use actix_web::{HttpResponse, web};
+use serde::Deserialize;
+
+use crate::api::response::{ApiErrorResponse, ApiListResponse};
+use crate::error::AppError;
+use crate::service::AppService;
+use crate::session::Session;
+
+#[derive(Deserialize, utoipa::IntoParams)]
+pub struct BillingHistoryQuery {
+    pub limit: Option<i64>,
+    pub offset: Option<i64>,
+}
+
+#[utoipa::path(
+    get,
+    path = "/api/v1/workspaces/{workspace_name}/billing/history",
+    tag = "Workspaces",
+    operation_id = "workspaceBillingHistory",
+    summary = "List billing history",
+    description = "Return billing history for a workspace. Requires owner role.",
+    params(
+        ("workspace_name" = String, Path, description = "Workspace name."),
+        BillingHistoryQuery
+    ),
+    responses(
+        (status = 200, description = "List of billing history entries (currently empty).", body = ApiListResponse<serde_json::Value>),
+        (status = 401, description = "Unauthenticated or insufficient role.", body = ApiErrorResponse),
+        (status = 500, description = "Internal server error.", body = ApiErrorResponse)
+    )
+)]
+pub async fn billing_history(
+    _service: web::Data<AppService>,
+    _session: Session,
+    _path: web::Path<String>,
+    _query: web::Query<BillingHistoryQuery>,
+) -> Result<HttpResponse, AppError> {
+    Ok(HttpResponse::Ok().json(ApiListResponse::<serde_json::Value>::empty()))
+}