feat: Review-Agent (Multi-Agent-Kommunikation)

- Session hat optionalen ReviewAgentId + MaxReviewIterations
- Nach end_turn des Worker-Agents wird der Review-Agent aufgerufen
- Review-Agent bekommt Worker-Konversation als Kontext + kann Tools nutzen
- [APPROVED] in Review-Antwort → fertig, sonst Feedback an Worker
- Worker korrigiert und wird erneut reviewed (max N Runden)
- SSE-Events: review_start, review_text, review_tool_use, review_feedback, review_approved
- Chat-UI: Review-Phase als eigene Bubble mit Header, Text, Status
- Session-Page: Review-Agent-Picker (gleicher Agent-Card-Helper)
- Dashboard: Review-Agent-Badge auf Session-Cards
- DB-Migration: review_agent_id, max_review_iterations auf sessions

Services/ChatService.cs

@@ -106,6 +106,42 @@ public class ChatService
         if (!string.IsNullOrWhiteSpace(systemPromptText))
             systemPrompt.Add(new { type = "text", text = systemPromptText });
 
+        // Review-Agent vorbereiten (falls konfiguriert)
+        ReviewContext reviewContext = null;
+        if (!string.IsNullOrEmpty(session.ReviewAgentId))
+        {
+            var reviewAgent = await _db.GetAgent(session.ReviewAgentId);
+            if (reviewAgent != null)
+            {
+                var reviewModelId = ResolveModelId(reviewAgent.Model);
+                var reviewMarked = await _db.GetMarkedMessages(sessionId);
+                var reviewMemDir = _memoryService.GetAgentMemoryDir(reviewAgent.AgentId);
+                var reviewSkills = await _db.GetAgentSkills(reviewAgent.AgentId);
+                var reviewWorkspace = workspace; // gleicher Workspace wie Worker
+                var reviewSystemText = SystemPromptBuilder.Build(
+                    reviewAgent, session, reviewMarked, _memoryService, reviewMemDir,
+                    reviewSkills, _skillService, userPersona: user?.GetEffectivePersona(),
+                    resolvedWorkspace: reviewWorkspace);
+
+                var reviewPrompt = new List<object>();
+                if (!string.IsNullOrWhiteSpace(reviewSystemText))
+                    reviewPrompt.Add(new { type = "text", text = reviewSystemText });
+
+                reviewContext = new ReviewContext
+                {
+                    ModelId = reviewModelId,
+                    SystemPrompt = reviewPrompt,
+                    AgentId = reviewAgent.AgentId,
+                    Workspace = reviewWorkspace,
+                    UseMemory = reviewAgent.UseMemory,
+                    WebSearchVersion = reviewAgent.WebSearchVersion,
+                    ToolChoice = reviewAgent.ToolChoice ?? "any",
+                    MaxReviewIterations = session.MaxReviewIterations > 0 ? session.MaxReviewIterations : 3,
+                    Agent = reviewAgent
+                };
+            }
+        }
+
         return new ChatContext
         {
             ChainId = chainId,
@@ -120,7 +156,8 @@ public class ChatService
             WebSearchVersion = agent.WebSearchVersion,
             MaxIterations = maxIterations,
             Agent = agent,
-            Session = session
+            Session = session,
+            Review = reviewContext
         };
     }