fix: 强制移除knowledge_bases表中的历史vlm_model_id字段

migrations/versioned/000004_drop_vlm_model_id.down.sql

@@ -0,0 +1,12 @@
+-- Migration: drop_vlm_model_id (rollback)
+-- Description: Re-add vlm_model_id column to knowledge_bases table
+
+DO $$ 
+BEGIN
+    RAISE NOTICE '[Migration 000004 Rollback] Re-adding vlm_model_id column to knowledge_bases table...';
+    
+    -- Re-add vlm_model_id column (nullable to avoid issues)
+    ALTER TABLE knowledge_bases ADD COLUMN IF NOT EXISTS vlm_model_id VARCHAR(64);
+    
+    RAISE NOTICE '[Migration 000004 Rollback] vlm_model_id column re-added successfully';
+END $$;

migrations/versioned/000004_drop_vlm_model_id.up.sql

@@ -0,0 +1,12 @@
+-- Migration: drop_vlm_model_id
+-- Description: Drop vlm_model_id column from knowledge_bases table (field moved to vlm_config JSON)
+
+DO $$ 
+BEGIN
+    RAISE NOTICE '[Migration 000004] Dropping vlm_model_id column from knowledge_bases table...';
+    
+    -- Drop vlm_model_id column if exists (this field was moved to vlm_config JSON)
+    ALTER TABLE knowledge_bases DROP COLUMN IF EXISTS vlm_model_id;
+    
+    RAISE NOTICE '[Migration 000004] vlm_model_id column dropped successfully';
+END $$;