* fix(feishu): require exact bot_open_id match for mention detection
- Previously, when bot_open_id was empty, ALL mentions were treated as bot mentions
- This caused multiple agents in same group to all respond to any mention
- Now requires bot_open_id to be set AND match exactly for mentionedBot=true
- Fixes issue where CPPAI PM would respond even when other agent was mentioned
* fix(feishu): gate group pairing by target bot
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Co-authored-by: ntduc <ntduc@cpp.ai.vn>