fix for stats and model selection

migrations/20260905090000_allow_qwen_session_model/down.sql

@@ -0,0 +1,13 @@
+ALTER TABLE sessions ADD COLUMN model_without_qwen TEXT
+    CHECK (model_without_qwen IS NULL OR model_without_qwen IN (
+        'deepseek-v4-flash-0731',
+        'deepseek-v4-pro',
+        'glm-5.2',
+        'glm-5.3-flash'
+    ));
+UPDATE sessions SET model_without_qwen = CASE
+    WHEN model = 'qwen3.8-flash-next' THEN NULL
+    ELSE model
+END;
+ALTER TABLE sessions DROP COLUMN model;
+ALTER TABLE sessions RENAME COLUMN model_without_qwen TO model;