Add WebhookEvent entity for tracking webhook deliveries

Author: nickprotop

cloud/src/LrmCloud.Api/Controllers/WebhooksController.cs

@@ -94,10 +94,35 @@ private async Task<IActionResult> HandleWebhookAsync(string providerName, string
             return BadRequest($"Missing {signatureHeader} header");
         }
 
+        // Collect additional headers for PayPal verification
+        var webhookHeaders = new Dictionary<string, string>();
+        if (providerName == "paypal")
+        {
+            // PayPal requires additional headers for webhook verification
+            var headerNames = new[]
+            {
+                "PAYPAL-AUTH-ALGO",
+                "PAYPAL-CERT-URL",
+                "PAYPAL-TRANSMISSION-ID",
+                "PAYPAL-TRANSMISSION-TIME",
+                "PAYPAL-TRANSMISSION-SIG"
+            };
+
+            foreach (var headerName in headerNames)
+            {
+                var value = Request.Headers[headerName].FirstOrDefault();
+                if (!string.IsNullOrEmpty(value))
+                {
+                    webhookHeaders[headerName] = value;
+                }
+            }
+        }
+
         try
         {
-            // Process webhook with provider
-            var result = await provider.ProcessWebhookAsync(payload, signature);
+            // Process webhook with provider (pass headers for PayPal verification)
+            var result = await provider.ProcessWebhookAsync(payload, signature,
+                webhookHeaders.Count > 0 ? webhookHeaders : null);
 
             if (!result.Success)
             {

cloud/src/LrmCloud.Api/Data/AppDbContext.cs

@@ -56,6 +56,9 @@ public AppDbContext(DbContextOptions<AppDbContext> options) : base(options)
     public DbSet<ProjectReviewer> ProjectReviewers => Set<ProjectReviewer>();
     public DbSet<OrganizationReviewer> OrganizationReviewers => Set<OrganizationReviewer>();
 
+    // Billing & Webhooks
+    public DbSet<WebhookEvent> WebhookEvents => Set<WebhookEvent>();
+
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
         base.OnModelCreating(modelBuilder);
@@ -518,6 +521,17 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
             // Match parent's soft-delete filter
             entity.HasQueryFilter(e => e.Organization!.DeletedAt == null);
         });
+
+        // =====================================================================
+        // Webhook Events (Idempotency)
+        // =====================================================================
+        modelBuilder.Entity<WebhookEvent>(entity =>
+        {
+            // Unique constraint to prevent duplicate processing
+            entity.HasIndex(e => new { e.ProviderEventId, e.ProviderName }).IsUnique();
+            entity.HasIndex(e => e.ProcessedAt);
+            entity.HasIndex(e => e.UserId);
+        });
     }
 
     /// <summary>