feat(service): expand service layer with new domain operations

- Add IM service modules: audit, channel roles, custom emojis, forum
  tags, integrations, invitations, repo links, slash commands, stages,
  voice, webhooks
- Add PR service modules: review requests, templates
- Add repo service modules: contributors, release assets, git extras
  (archive, branch rename, commit extras, diff/merge, tag, tree)
- Add user service: social (follow/block)
- Add internal auth service
- Update existing service modules with expanded functionality
- Remove deleted IM modules: articles, delivery trace, drafts,
  follows, messages, polls, presence, reactions, threads

service/auth/email.rs

@@ -35,6 +35,7 @@ struct PendingEmailChange {
 impl AuthService {
     const EMAIL_CHANGE_PREFIX: &'static str = "auth:email_change:";
     const EMAIL_CHANGE_TTL_SECS: u64 = 60 * 60;
+    const EMAIL_CHANGE_COOLDOWN_SECS: u64 = 60;
 
     pub async fn auth_get_email(&self, ctx: &Session) -> Result<EmailResponse, AppError> {
         let user_uid = ctx.user().ok_or(AppError::Unauthorized)?;
@@ -63,11 +64,20 @@ impl AuthService {
         if new_email.is_empty() {
             return Err(AppError::BadRequest("email is required".into()));
         }
+
+        // Rate limiting: check cooldown
+        let cooldown_key = format!("{}cooldown:{}", Self::EMAIL_CHANGE_PREFIX, user_uid);
+        if self.ctx.cache.exists(&cooldown_key).await {
+            return Err(AppError::BadRequest(
+                "email change request was sent recently; please try again later".into(),
+            ));
+        }
+
         let password = self.auth_rsa_decode(ctx, params.password).await?;
 
         let row = sqlx::query("SELECT password_hash FROM user_password WHERE user_id = $1")
             .bind(user_uid)
-            .fetch_optional(self.ctx.db.reader())
+            .fetch_optional(self.ctx.db.writer())
             .await
             .map_err(AppError::Database)?
             .ok_or(AppError::UserNotFound)?;
@@ -103,6 +113,7 @@ impl AuthService {
                 },
                 Some(Duration::from_secs(Self::EMAIL_CHANGE_TTL_SECS)),
             )
+            .await
             .map_err(|e| AppError::InternalServerError(e.to_string()))?;
 
         let domain = self.ctx.config.main_domain()?;
@@ -133,6 +144,16 @@ impl AuthService {
             AppError::InternalServerError(e.to_string())
         })?;
 
+        // Set cooldown after successful email send
+        let cooldown_key = format!("{}cooldown:{}", Self::EMAIL_CHANGE_PREFIX, user_uid);
+        if let Err(e) = self.ctx.cache.set(
+            &cooldown_key,
+            &true,
+            Some(Duration::from_secs(Self::EMAIL_CHANGE_COOLDOWN_SECS)),
+        ).await {
+            tracing::warn!(error = %e, "Failed to set email change cooldown");
+        }
+
         tracing::info!(new_email = %new_email, user_uid = %user_uid, "Email change verification sent");
         Ok(())
     }
@@ -148,6 +169,7 @@ impl AuthService {
             self.ctx
                 .cache
                 .get::<PendingEmailChange>(&cache_key)
+                .await
                 .ok_or(AppError::NotFound(
                     "invalid or expired email verification token".into(),
                 ))?;
@@ -195,7 +217,7 @@ impl AuthService {
 
         txn.commit().await.map_err(|_| AppError::TxnError)?;
 
-        let _ = self.ctx.cache.delete(&cache_key);
+        let _ = self.ctx.cache.delete(&cache_key).await;
         tracing::info!(new_email = %pending.new_email, user_uid = %pending.user_uid, "Email changed");
         Ok(())
     }