Pure functions for WebSocket authentication logic.

Following FC/IS pattern - all functions are pure (no I/O).
JWT token extraction and validation logic.
Actual JWT verification delegated to shell/ports.

Pure functions for WebSocket connection state management.

Following FC/IS pattern - all functions are pure (no I/O).
Connection lifecycle and authorization logic.

Pure functions for WebSocket message validation and routing.

Following FC/IS pattern - all functions are pure (no I/O).
Message creation, validation, and routing logic.

Pure functions for pub/sub topic management.

Implements topic-based message routing where connections can subscribe to
topics and receive messages published to those topics. All functions are pure
(no I/O, no side effects) following FC/IS pattern.

Key Features:
- Subscribe connection to topic (add to subscription set)
- Unsubscribe connection from topic (remove from set)
- Find all subscribers for topic (set intersection)
- Clean up subscriptions on disconnect (remove all for connection)

Data Structure:
Subscriptions are represented as a map:
{topic-name #{connection-id-1 connection-id-2 ...}}