refactor(models): update data models and remove deprecated IM entities

- Update channel, notification, PR, repo, user, workspace models
- Remove deleted IM models: articles, channel follows, message
  attachments/bookmarks/drafts/edit history/embeds/mentions/pins/
  polls/reactions/threads, saved messages, thread read states
- Add new PR models: review requests, templates
- Add repo release assets model
- Add base_info module for API detail responses

models/notifications/notification_templates.rs

@@ -3,7 +3,7 @@ use chrono::{DateTime, Utc};
 use serde::{Deserialize, Serialize};
 use uuid::Uuid;
 
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, sqlx::FromRow)]
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, sqlx::FromRow, utoipa::ToSchema)]
 pub struct NotificationTemplate {
     pub id: Uuid,
     pub key: String,