Don't reference DM memories in group chat responses

When Ava responded to Kate's group chat message about Florida vacations, she said "based on ben's research from earlier" - referencing a private DM conversation Ben had with Ava the day before.

This is a privacy issue: DM conversations should not leak into group chat responses.

Current behavior: The agent's context/memory system pulls from all conversations when generating responses, including private DMs.

Expected behavior: When responding in a group chat, Ava should only use:

• Group chat history for that specific group
• General knowledge/facts
• NOT private DM conversations with individual users

Investigation needed: 1. Check how getAdaptiveContext and getGroupConversationContext work 2. Determine if the memory/RAG system is pulling DM content into group responses 3. May need to filter memories by chat context or add a "private" flag to DM-sourced memories

Files to check:

• Omni/Agent/Memory.hs - context retrieval functions
• Omni/Agent/Telegram.hs - how context is passed to agent

Privacy implications: Users may share sensitive info in DMs they don't want surfaced in group chats.