Vorgaenge in der WebUI: entscheiden und Stellungnahme anfordern (#689, Stufe 3)

- /api/cases (offen/alle), /api/cases/{id}/decide, /api/cases/{id}/statement, /api/decisions
- Ansicht "Vorgaenge": offene Faelle mit Verlauf je Ebene (Lauf-Links), Frist und
  "Mensch gerufen"; Reiter Beschluesse mit Reichweite; Zaehler in der Seitenleiste
- Konzept Abschnitt 5: Umsetzung

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ClawdDotNet.Web/Contracts/CaseDtos.cs

@@ -0,0 +1,43 @@
+namespace ClawdDotNet.Web.Contracts;
+
+/// <summary>#689: A case — escalation or conflict — with everything each level said.</summary>
+public sealed record CaseDto(
+    string Id,
+    string Kind,
+    string Status,
+    string Subject,
+    string OpenedBy,
+    DateTime OpenedAt,
+    DateTime DeadlineUtc,
+    DateTime? HumanCalledAt,
+    // null: a human holds it.
+    string? Holder,
+    string HolderTaskId,
+    int Level,
+    string OriginTaskId,
+    string OriginRunId,
+    IReadOnlyList<string> Parties,
+    IReadOnlyList<string> Informed,
+    IReadOnlyList<string> WaitingFor,
+    IReadOnlyList<CaseEntryDto> Trail,
+    string? DecisionId);
+
+public sealed record CaseEntryDto(DateTime At, string Author, string Kind, string Text, string? RunId);
+
+public sealed record DecisionDto(
+    string Id,
+    string Subject,
+    string Question,
+    string Answer,
+    string Reasoning,
+    string DecidedBy,
+    DateTime DecidedAt,
+    string? ScopeUnitId,
+    // "Purchasing / Team A"; null: binds the whole instance.
+    string? ScopePath,
+    string CaseId,
+    string? RunId);
+
+public sealed record CaseDecisionInputDto(string? Answer, string? Reasoning);
+
+public sealed record CaseStatementInputDto(string? AgentId, string? Question);