fix(mcp): register ticket import tools in the external MCP container

The external MCP server has its own DI container; TicketMcpTools could not
resolve TicketImportService there, so both tools failed at runtime. Also
surface a skipped import in the prime outcome and treat a sweep where every
project board fails as an error instead of an empty backlog.

src/ClaudeDo.Worker/Tickets/TicketImportService.cs

@@ -200,6 +200,8 @@ public sealed class TicketImportService
         var identity = await client.GetIdentityAsync(ct);
         var projects = await client.GetProjectsAsync(ct);
         var items = new List<TicketCandidate>();
+        string? lastFailure = null;
+        var failed = 0;
 
         foreach (var project in projects)
         {
@@ -212,6 +214,8 @@ public sealed class TicketImportService
             {
                 // Ein unlesbares Board darf den Sweep über die übrigen Projekte nicht abbrechen.
                 _logger.LogWarning("Board von Projekt {project_id} übersprungen: {reason}", project.Id, ex.Message);
+                lastFailure = ex.Message;
+                failed++;
                 continue;
             }
 
@@ -233,6 +237,10 @@ public sealed class TicketImportService
             }
         }
 
+        // Scheitern ALLE Boards (z.B. Scope fehlt), ist das ein Fehler — kein leerer Backlog.
+        if (projects.Count > 0 && failed == projects.Count)
+            throw new TicketApiException($"Kein Projekt-Board lesbar: {lastFailure}");
+
         return (items.DistinctBy(i => i.Id).ToList(), projects);
     }