fix: token统计+聊天记录入库静默失败, 列名/类型/去重不匹配

根因：insert_llm_usage / insert_chat_record 因旧 iPet 遗留列 (kind/entry NOT NULL,
context_token_present boolean→context_token text) 导致 INSERT 静默失败,
四个调用点 let _ = 吞掉错误。ias usage 显示 token 总量为 0。

修复：
- llm_usage: 迁移 0010 ADD COLUMN IF NOT EXISTS + 条件 DROP NOT NULL,
  insert_llm_usage 写入 kind/entry 默认值
- chat_records: 迁移 0011 列名 context_token_present→context_token 类型转换+重命名,
  迁移 0012 清理存量重复→partial UNIQUE index→恢复 ON CONFLICT
- main.rs: 所有 let _ = insert_* 改为 if let Err(e) 日志输出,
  message_id 缺失时归为 '' 而非 '0'

migrations/20260601000010_fix_llm_usage_legacy_columns.sql

@@ -0,0 +1,18 @@
+-- 修复 llm_usage 表兼容性：旧库有 iPet 遗留的 kind/entry 列 (NOT NULL)，新库没有
+-- kind/entry 保留为兼容字段，新代码写入默认值 ("llm_call" / null)
+-- 1) 添加列（如果不存在）
+ALTER TABLE llm_usage ADD COLUMN IF NOT EXISTS kind TEXT;
+ALTER TABLE llm_usage ADD COLUMN IF NOT EXISTS entry JSONB;
+-- 2) 只在列存在且 NOT NULL 时解除约束
+DO $$
+BEGIN
+    IF EXISTS (SELECT 1 FROM information_schema.columns
+               WHERE table_name = 'llm_usage' AND column_name = 'kind' AND is_nullable = 'NO') THEN
+        ALTER TABLE llm_usage ALTER COLUMN kind DROP NOT NULL;
+    END IF;
+    IF EXISTS (SELECT 1 FROM information_schema.columns
+               WHERE table_name = 'llm_usage' AND column_name = 'entry' AND is_nullable = 'NO') THEN
+        ALTER TABLE llm_usage ALTER COLUMN entry DROP NOT NULL;
+    END IF;
+END;
+$$;