feat(backend): add communication, tester, admin and middleman modules

Implement step 17 modules: threads/messages, notifications with automation (submission.created, idea.created, grant_call.opened), innovation test feedback, admin panel (submissions, verify, metrics, grant call status), Middleman adaptation and partnerships. Split multi-type files into one type per file and replace object-valued dictionaries with string-valued maps in data contracts (migrations 0006/0007).

backend/Application/Abstractions/AdminContracts.cs

@@ -0,0 +1,18 @@
+using TarninaHub.Application.Dtos;
+
+namespace TarninaHub.Application.Abstractions;
+
+public interface IAdminService
+{
+    Task<IReadOnlyList<SubmissionResponse>> ListSubmissionsAsync(
+        string? status,
+        string? challengeId,
+        CancellationToken cancellationToken);
+
+    Task<KnowledgeItemResponse?> VerifyKnowledgeItemAsync(
+        string knowledgeItemId,
+        VerifyKnowledgeItemRequest request,
+        CancellationToken cancellationToken);
+
+    Task<AdminMetricsResponse> GetMetricsAsync(CancellationToken cancellationToken);
+}