feat(fase4): add AI response and sentiment nodes

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

services/flow-engine/app/nodes/__init__.py

@@ -1,6 +1,18 @@
+from app.nodes.advanced import (
+    DelayExecutor,
+    GoToExecutor,
+    LoopExecutor,
+    RandomExecutor,
+    SwitchExecutor,
+)
+from app.nodes.ai import AIResponseExecutor, AISentimentExecutor
 from app.nodes.base import NodeExecutor, NodeRegistry
 from app.nodes.basic import (
-    TriggerExecutor, MessageExecutor, ButtonsExecutor,
-    WaitInputExecutor, SetVariableExecutor, ConditionExecutor
+    ButtonsExecutor,
+    ConditionExecutor,
+    MessageExecutor,
+    SetVariableExecutor,
+    TriggerExecutor,
+    WaitInputExecutor,
 )
-from app.nodes.script import JavaScriptExecutor, HttpRequestExecutor
+from app.nodes.script import HttpRequestExecutor, JavaScriptExecutor