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/Dtos/SubmissionResponse.cs

@@ -0,0 +1,17 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace TarninaHub.Application.Dtos;
+
+
+public sealed record SubmissionResponse(
+    string Id,
+    string ProblemId,
+    string Title,
+    string Description,
+    string ChallengeId,
+    string LocationId,
+    string AuthorId,
+    string Status,
+    IReadOnlyList<string> Keywords,
+    DateTimeOffset CreatedAt,
+    DateTimeOffset? UpdatedAt);