perf(04-01): eliminate N+1 on endpoint list queries via Select projection

- Add EndpointListItem projection DTO to EndpointRepository
- Rewrite ListAllAsync and ListByAppIdAsync with Select projection (no Include EventTypes)
- Update DashboardEndpointController.ListEndpoints to map from EndpointListItem
- Add ToDto(EndpointListItem) overload in ApiResponseMapper for EndpointsController compatibility
- API response shapes unchanged for both dashboard and public endpoints

Author: voyvodka

src/WebhookEngine.API/Contracts/ApiResponseDtos.cs

@@ -1,5 +1,6 @@
 using System.Text.Json;
 using WebhookEngine.Core.Entities;
+using WebhookEngine.Infrastructure.Repositories;
 using EndpointEntity = WebhookEngine.Core.Entities.Endpoint;
 
 namespace WebhookEngine.API.Contracts;
@@ -94,6 +95,24 @@ public static EndpointResponseDto ToDto(this EndpointEntity endpoint)
         };
     }
 
+    public static EndpointResponseDto ToDto(this EndpointListItem endpoint)
+    {
+        return new EndpointResponseDto
+        {
+            Id = endpoint.Id,
+            AppId = endpoint.AppId,
+            Url = endpoint.Url,
+            Description = endpoint.Description,
+            Status = endpoint.Status.ToString().ToLowerInvariant(),
+            CustomHeadersJson = JsonValueParser.ParseOrEmptyObject(endpoint.CustomHeadersJson),
+            SecretOverride = endpoint.SecretOverride,
+            MetadataJson = JsonValueParser.ParseOrEmptyObject(endpoint.MetadataJson),
+            FilterEventTypes = endpoint.EventTypeIds,
+            CreatedAt = endpoint.CreatedAt,
+            UpdatedAt = endpoint.UpdatedAt
+        };
+    }
+
     public static MessageResponseDto ToDto(this Message message)
     {
         return new MessageResponseDto

src/WebhookEngine.API/Controllers/DashboardEndpointController.cs

@@ -54,13 +54,13 @@ public async Task<IActionResult> ListEndpoints(
             {
                 id = e.Id,
                 appId = e.AppId,
-                appName = e.Application?.Name,
+                appName = e.AppName,
                 url = e.Url,
                 description = e.Description,
                 status = e.Status.ToString().ToLowerInvariant(),
-                circuitState = e.Health?.CircuitState.ToString().ToLowerInvariant() ?? "closed",
-                eventTypes = e.EventTypes.Select(et => et.Name).ToList(),
-                eventTypeIds = e.EventTypes.Select(et => et.Id).ToList(),
+                circuitState = (e.CircuitState ?? "closed").ToLowerInvariant(),
+                eventTypes = e.EventTypeNames,
+                eventTypeIds = e.EventTypeIds,
                 createdAt = e.CreatedAt,
                 updatedAt = e.UpdatedAt
             }),

src/WebhookEngine.Infrastructure/Repositories/EndpointRepository.cs

@@ -32,7 +32,7 @@ public EndpointRepository(WebhookDbContext dbContext)
             .FirstOrDefaultAsync(e => e.AppId == appId && e.Id == id, ct);
     }
 
-    public async Task<List<Endpoint>> ListByAppIdAsync(
+    public async Task<List<EndpointListItem>> ListByAppIdAsync(
         Guid appId,
         EndpointStatus? status,
         int page,
@@ -41,8 +41,6 @@ public async Task<List<Endpoint>> ListByAppIdAsync(
     {
         var query = _dbContext.Endpoints
             .AsNoTracking()
-            .Include(e => e.Health)
-            .Include(e => e.EventTypes)
             .Where(e => e.AppId == appId)
             .AsQueryable();
 
@@ -52,6 +50,23 @@ public async Task<List<Endpoint>> ListByAppIdAsync(
         }
 
         return await query
+            .Select(e => new EndpointListItem
+            {
+                Id = e.Id,
+                AppId = e.AppId,
+                AppName = e.Application != null ? e.Application.Name : null,
+                Url = e.Url,
+                Description = e.Description,
+                Status = e.Status,
+                CircuitState = e.Health != null ? e.Health.CircuitState.ToString() : null,
+                CustomHeadersJson = e.CustomHeadersJson,
+                SecretOverride = e.SecretOverride,
+                MetadataJson = e.MetadataJson,
+                EventTypeNames = e.EventTypes.Select(et => et.Name).ToList(),
+                EventTypeIds = e.EventTypes.Select(et => et.Id).ToList(),
+                CreatedAt = e.CreatedAt,
+                UpdatedAt = e.UpdatedAt
+            })
             .OrderByDescending(e => e.CreatedAt)
             .Skip((page - 1) * pageSize)
             .Take(pageSize)
@@ -110,9 +125,10 @@ await _dbContext.Endpoints
     }
 
     /// <summary>
-    /// Cross-app list for dashboard admin — returns endpoints across all applications.
+    /// Cross-app list for dashboard admin — returns endpoints across all applications
+    /// using Select projection to avoid N+1 on EventTypes.
     /// </summary>
-    public async Task<List<Endpoint>> ListAllAsync(
+    public async Task<List<EndpointListItem>> ListAllAsync(
         Guid? appId,
         EndpointStatus? status,
         int page,
@@ -121,9 +137,6 @@ public async Task<List<Endpoint>> ListAllAsync(
     {
         var query = _dbContext.Endpoints
             .AsNoTracking()
-            .Include(e => e.Application)
-            .Include(e => e.Health)
-            .Include(e => e.EventTypes)
             .AsQueryable();
 
         if (appId.HasValue)
@@ -133,6 +146,23 @@ public async Task<List<Endpoint>> ListAllAsync(
             query = query.Where(e => e.Status == status.Value);
 
         return await query
+            .Select(e => new EndpointListItem
+            {
+                Id = e.Id,
+                AppId = e.AppId,
+                AppName = e.Application != null ? e.Application.Name : null,
+                Url = e.Url,
+                Description = e.Description,
+                Status = e.Status,
+                CircuitState = e.Health != null ? e.Health.CircuitState.ToString() : null,
+                CustomHeadersJson = e.CustomHeadersJson,
+                SecretOverride = e.SecretOverride,
+                MetadataJson = e.MetadataJson,
+                EventTypeNames = e.EventTypes.Select(et => et.Name).ToList(),
+                EventTypeIds = e.EventTypes.Select(et => et.Id).ToList(),
+                CreatedAt = e.CreatedAt,
+                UpdatedAt = e.UpdatedAt
+            })
             .OrderByDescending(e => e.CreatedAt)
             .Skip((page - 1) * pageSize)
             .Take(pageSize)
@@ -152,3 +182,21 @@ public async Task<int> CountAllAsync(Guid? appId, EndpointStatus? status, Cancel
         return await query.CountAsync(ct);
     }
 }
+
+public record EndpointListItem
+{
+    public Guid Id { get; init; }
+    public Guid AppId { get; init; }
+    public string? AppName { get; init; }
+    public string Url { get; init; } = string.Empty;
+    public string? Description { get; init; }
+    public EndpointStatus Status { get; init; }
+    public string? CircuitState { get; init; }
+    public string CustomHeadersJson { get; init; } = "{}";
+    public string? SecretOverride { get; init; }
+    public string MetadataJson { get; init; } = "{}";
+    public List<string> EventTypeNames { get; init; } = [];
+    public List<Guid> EventTypeIds { get; init; } = [];
+    public DateTime CreatedAt { get; init; }
+    public DateTime UpdatedAt { get; init; }
+}