feat: Agent-Einstellung 'Rückfragen erlauben' (allowUserChoice)

- Neues Feld AllowUserChoice (bool, default true) im AgentRecord
- DB-Migration: allow_user_choice Spalte mit DEFAULT 1
- Agent-Form: Checkbox 'Rückfragen erlauben' nach 'Tool-Nutzung erzwingen'
- ToolService.GetToolDefinitions: neuer Parameter includeUserChoice
- ask_user_choice Tool wird nur eingebunden wenn Agent es erlaubt
- Review-Agents und Non-Streaming (Cronjobs) erhalten nie ask_user_choice
- ChatEndpoint reicht Agent.AllowUserChoice an StreamChat durch

wwwroot/js/pages/agent-page.js

@@ -18,6 +18,7 @@ registerPage('agent', {
     const descEl = document.getElementById('agentDescription');
     const modelEl = document.getElementById('agentModel');
     const toolChoiceEl = document.getElementById('agentToolChoice');
+    const allowUserChoiceEl = document.getElementById('agentAllowUserChoice');
     const autoCommitEl = document.getElementById('agentAutoCommit');
     const useSoulEl = document.getElementById('agentUseSoul');
     const useIdentityEl = document.getElementById('agentUseIdentity');
@@ -49,6 +50,7 @@ registerPage('agent', {
       descEl.value = agent.description || '';
       modelEl.value = agent.model || 'sonnet';
       toolChoiceEl.checked = (agent.toolChoice || 'any') === 'any';
+      allowUserChoiceEl.checked = agent.allowUserChoice !== false;
       autoCommitEl.value = agent.autoCommit || '';
       useSoulEl.checked = agent.useSoul !== false;
       useIdentityEl.checked = agent.useIdentity !== false;
@@ -94,6 +96,7 @@ registerPage('agent', {
         description: descEl.value.trim(),
         model: modelEl.value,
         toolChoice: toolChoiceEl.checked ? 'any' : 'auto',
+        allowUserChoice: allowUserChoiceEl.checked,
         autoCommit: autoCommitEl.value,
         useSoul: useSoulEl.checked,
         useIdentity: useIdentityEl.checked,