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/css/chat.css

@@ -1145,15 +1145,6 @@
   max-width: 80%;
   display: flex;
   flex-direction: column;
-  gap: var(--box-spacing);
-}
-
-.choice-question {
-  font-size: 0.95em;
-}
-
-.choice-question p {
-  margin: 0;
 }
 
 .choice-buttons {
@@ -1163,24 +1154,15 @@
 }
 
 .choice-btn {
-  padding: 0.45em 1em;
   border: var(--border-width) solid var(--primary);
   border-radius: var(--border-radius);
   background: transparent;
   color: var(--primary);
-  font-size: 0.9em;
-  cursor: pointer;
-  transition: all 0.15s ease;
-  font-family: inherit;
 }
 
 .choice-btn:hover:not(:disabled) {
   background: var(--primary);
-  color: var(--primary-text);
-}
-
-.choice-btn:active:not(:disabled) {
-  transform: scale(0.97);
+  color: var(--f1-bg);
 }
 
 .choice-btn:disabled {
@@ -1189,17 +1171,12 @@
 
 .choice-btn.choice-selected {
   background: var(--primary);
-  color: var(--primary-text);
+  color: var(--f1-bg);
   border-color: var(--primary);
-  font-weight: 600;
 }
 
 .choice-btn.choice-unselected {
-  opacity: 0.4;
+  opacity: var(--semi-transparent);
   border-color: var(--f1-border);
   color: var(--muted);
 }
-
-.choice-answered .choice-question {
-  opacity: 0.7;
-}