perf: backend storage/admin queries without loading all documents (#2)

backend/src/main/java/com/crystalpdf/backend/config/AdminDataInitializer.java

@@ -25,7 +25,7 @@ ApplicationRunner seedAdmin(
             // Credentials are read from application.yml (environment-configurable).
             // Once created, admin password is not auto-reset (prevent privilege escalation).
             // To recover a lost admin password, manually set a new one via database or admin console.
-            boolean adminExists = userRepo.findAll().stream().anyMatch(User::isAdmin);
+            boolean adminExists = userRepo.existsByAdminTrue();
             if (!adminExists) {
                 User admin = new User();
                 admin.setEmail(adminEmail);

backend/src/main/java/com/crystalpdf/backend/repository/DocumentRepository.java

@@ -2,11 +2,19 @@
 
 import com.crystalpdf.backend.entity.Document;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 
 import java.util.List;
 import java.util.Optional;
 
 public interface DocumentRepository extends JpaRepository<Document, Long> {
     List<Document> findByOwnerIdOrderByCreatedAtDesc(Long userId);
     Optional<Document> findByIdAndOwnerId(Long id, Long userId);
+
+    /** Sum storage without loading every Document row (list endpoint / quota checks). */
+    @Query("select coalesce(sum(d.sizeBytes), 0) from Document d where d.owner.id = :ownerId")
+    long sumSizeBytesByOwnerId(@Param("ownerId") Long ownerId);
+
+    long countByOwner_Id(Long ownerId);
 }

backend/src/main/java/com/crystalpdf/backend/repository/UserRepository.java

@@ -9,5 +9,7 @@ public interface UserRepository extends JpaRepository<User, Long> {
     Optional<User> findByEmail(String email);
     boolean existsByEmail(String email);
     Optional<User> findByUsername(String username);
+    boolean existsByAdminTrue();
+    long countByAdminTrue();
     boolean existsByUsername(String username);
 }

backend/src/main/java/com/crystalpdf/backend/service/AdminService.java

@@ -68,15 +68,15 @@ public Page<AdminUserResponse> getAllUsers(int page, int pageSize, String search
 
         // Convert to responses
         List<AdminUserResponse> responses = allUsers.stream().map(user -> {
-            List<Document> docs = documentRepository.findByOwnerIdOrderByCreatedAtDesc(user.getId());
-            long storageUsed = docs.stream().mapToLong(Document::getSizeBytes).sum();
+            long storageUsed = documentRepository.sumSizeBytesByOwnerId(user.getId());
+            int documentCount = (int) documentRepository.countByOwner_Id(user.getId());
             AppSettings settings = getSettingsEntity();
             long limitBytes = user.getStorageLimitBytes() != null ? user.getStorageLimitBytes()
                     : settings.getDefaultStorageLimitMb() * 1024L * 1024L;
             return new AdminUserResponse(
                     user.getId(), user.getEmail(), user.getDisplayUsername(),
                     user.isAdmin(), user.isPasswordChangeRequired(),
-                    limitBytes, storageUsed, docs.size(),
+                    limitBytes, storageUsed, documentCount,
                     user.getCreatedAt() != null ? user.getCreatedAt().toString() : ""
             );
         }).toList();
@@ -167,7 +167,7 @@ public Map<String, Object> getSystemInfo() {
         // Platform stats
         info.put("totalUsers", userRepository.count());
         info.put("totalFiles", documentRepository.count());
-        info.put("totalAdmins", userRepository.findAll().stream().filter(User::isAdmin).count());
+        info.put("totalAdmins", userRepository.countByAdminTrue());
         info.put("javaVersion", System.getProperty("java.version"));
         info.put("osName", System.getProperty("os.name"));
 

backend/src/main/java/com/crystalpdf/backend/service/StorageService.java

@@ -70,9 +70,8 @@ public Document store(MultipartFile file, User owner) throws IOException {
                     settings.getMaxUploadSizeMb() + " MB.");
         }
 
-        // Check storage limit
-        List<Document> existingDocs = documentRepository.findByOwnerIdOrderByCreatedAtDesc(owner.getId());
-        long usedBytes = existingDocs.stream().mapToLong(Document::getSizeBytes).sum();
+        // Check storage limit (aggregate query — avoid loading all document rows)
+        long usedBytes = documentRepository.sumSizeBytesByOwnerId(owner.getId());
         long limitBytes = owner.getStorageLimitBytes() != null ? owner.getStorageLimitBytes()
                 : settings.getDefaultStorageLimitMb() * 1024L * 1024L;
         if (usedBytes + fileSizeBytes > limitBytes) {