* fix(feishu): enrich reply context for card and file replies
* refactor(feishu): extract reply functions to feishu_reply.go
- Move reply-related functions to new feishu_reply.go
- Move corresponding tests to feishu_reply_test.go
- Extract magic number 600 to maxReplyContextLen constant
- Unify replyTargetID/replyTargetFromMessage (prefer parent_id, fallback root_id)
- Add source comment for containsFeishuUpgradePlaceholder
* fix(feishu): skip API fallback for non-thread messages, prepend replied media refs
- resolveReplyTargetMessageID: only call fetchMessageByID fallback when
ThreadId is set, avoiding unnecessary API calls for non-reply messages
- prependReplyContext: prepend replied media refs before current media refs
to maintain correct ordering
* fix(feishu): add message cache for fetchMessageByID to avoid repeated downloads
- Add messageCache (sync.Map) to FeishuChannel struct
- Cache fetched messages with 30s TTL to avoid re-downloading attachments
when multiple users reply to the same parent message in a thread
- Cleanup expired entries on read access (no background goroutine needed)
* fix(feishu): early-return for non-reply messages, add cache and fetchMessageByID comment
* fix: remove duplicate test and fix gci import order
* fix(feishu): remove duplicate prependReplyContext call
ywj