chore(review): 移除 Copilot 指令，仅保留 Claude 与 PR 模板规则

删除 .github/copilot-instructions.md，CLAUDE.md 中不再引用 Copilot 规则。

Author: niexiaorong

.github/copilot-instructions.md

@@ -99,7 +99,7 @@ When a pull request changes the following version variables in `default.env` / `
 
 If the SQL init files are modified, run `node scripts/check-init-sql.js` to catch column/value mismatches. Any compose change must pass `docker compose config`.
 
-These rules are also encoded in `.github/copilot-instructions.md` and `.github/pull_request_template.md`.
+These rules are also encoded in `.github/pull_request_template.md`.
 
 ## Important Notes