IAV-1324/feat(memory): add agent-scoped Phase 3 facts pipeline and prompt injection
- Add Agent.facts / Agent.lastFactsAt and expose facts in MemoryContextResponse.
- Add async ConversationFactsGenerator with per-agent locking and prompt-processing /generate-conversation-facts integration (ConversationFactsResponse DTO).
- Add AgentLookupRepository REQUIRES_NEW helpers to update/load facts safely in async flows.
- Update ConversationMemoryServiceImpl to append agent facts to effective system prompt and include facts tokens in effective history budget calculation.