Remove dead store-and-forward and message aggregation code (#438)

- Remove completely unused message aggregation system (100% dead code)
- Remove broken store-and-forward implementation that only worked for relayed messages to offline favorites
- Update documentation to reflect actual functionality
- Net reduction of 312 lines of unmaintained code

Co-authored-by: jack <jackjackbits@users.noreply.github.com>

AI_CONTEXT.md

@@ -10,7 +10,6 @@ BitChat is a decentralized, peer-to-peer messaging application that works over B
 - **Bluetooth Mesh Networking**: Multi-hop message relay over BLE
 - **Privacy-First Design**: No accounts, no persistent identifiers
 - **End-to-End Encryption**: Uses Noise Protocol Framework for private messages
-- **Store & Forward**: Messages cached for offline peers
 - **IRC-Style Commands**: Familiar `/msg`, `/who` interface
 - **Cross-Platform**: Native iOS and macOS support
 - **Nostr Integration**: Seamless fallback for mutual favorites when out of Bluetooth range
@@ -142,7 +141,6 @@ BitChat is a decentralized, peer-to-peer messaging application that works over B
 - **No Long-Term Identifiers**: Enhances privacy and deniability
 
 ### 3. Mesh Networking
-- **Store & Forward**: Essential for intermittent connectivity
 - **TTL-Based Routing**: Prevents infinite loops in mesh
 - **Bloom Filters**: Efficient duplicate detection