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/Infrastructure/Persistence/IdeaService.cs

@@ -93,6 +93,19 @@ public sealed class IdeaService : IIdeaService
         return result;
     }
 
+    public async Task<IReadOnlyList<string>> ListDistinctAuthorIdsAsync(CancellationToken cancellationToken)
+    {
+        var response = await _client.RawQuery(
+            "SELECT type::string(author) AS id FROM idea;",
+            new Dictionary<string, object?>(),
+            cancellationToken);
+        response.EnsureAllOks();
+
+        var rows = response.GetValue<List<IdRow>>(0) ?? [];
+
+        return rows.Select(row => row.Id).Distinct(StringComparer.Ordinal).ToList();
+    }
+
     public async Task<IdeaResponse?> UpdateAsync(
         string ideaId,
         UpdateIdeaRequest request,