performance improvement and dedicated system workspace with no counter

[moneya]

Implement managed chat subscription synchronization and deduplication

• Introduce ManagedChatSubscriptionSyncRequest to encapsulate subscription parameters.
• Enhance Nip28ChatLaneWorker to store the last subscription sync request and prevent redundant commands.
• Update sync_managed_chat_subscriptions method to only send commands when subscription parameters change.
• Add unit tests to verify normalization of inputs and deduplication behavior in subscription requests.
• Create documentation for NIP-28 group chat performance issues and Jira ticket tracking.

Add system channel ID handling and update environment configuration

• Introduced system_channel_id to AutopilotChatState for managing system channels. - Updated methods to filter out system channels from active managed chat channels.
• Added new environment variable OA_NIP28_TEAM_CHANNEL_ID in .env.example.
• Enhanced rebuild_managed_chat_projection to exclude system channels from unread and mention counts.
• Documented progress on NIP-28 group chat performance improvements in related documentation.

Refactor NIP-28 chat lane subscription handling

• Introduced since_created_at filtering in TestNip28RelayFilter to manage event subscriptions based on creation time.
• Added TestNip28SubscriptionFrame to track subscription requests and closures, enhancing state management.
• Updated Nip28ChatLaneState to include requested_backfill_since_created_at and subscribed_backfill_since_created_at for better backfill handling.
• Refactored methods to utilize the new subscription management logic, ensuring cleaner state transitions and improved performance.
• Renamed subscription_since_created_at to reconnect_backfill_since_created_at for clarity in the ManagedChatProjectionState and related functions.