feat: GET /users (search/list) and GET /users/count

crates/adapters/postgres/src/user.rs

@@ -176,6 +176,13 @@ impl UserRepository for PgUserRepository {
             following_count: r.following_count,
         }).collect())
     }
+
+    async fn count(&self) -> Result<i64, DomainError> {
+        sqlx::query_scalar::<_, i64>("SELECT COUNT(*) FROM users WHERE local = true")
+            .fetch_one(&self.pool)
+            .await
+            .map_err(|e| DomainError::Internal(e.to_string()))
+    }
 }
 
 #[cfg(test)]