…ec to 0.2.0

Major Architectural Changes:

1. **Version Updates**:
   - Bumped rmqtt-codec from 0.1.2 to 0.2.0 (major version change)
   - Updated workspace dependency to use rmqtt-codec 0.2

2. **Type Separation**:
   - **CodecPublish**: Raw MQTT packet structure used for encoding/decoding
     - Removed `delay_interval` and `create_time` fields (broker concerns)
     - Simplified serialization/deserialization
   - **Publish**: Broker-level structure with additional metadata
     - Added `target_clientid`, `delay_interval`, and `create_time` fields
     - Provides higher-level functionality for broker operations

3. **Key Improvements**:
   - **Separation of Concerns**: Codec layer now purely handles MQTT protocol
   - **Broker Features**: Delay publishing and creation timestamps moved to broker level
   - **Type Safety**: Clear distinction between wire format and broker representation
   - **Performance**: Reduced codec complexity and memory footprint

4. **API Changes**:
   - Added `Deref` and `DerefMut` implementations for seamless access to inner fields
   - New builder methods: `target_clientid()`, `delay_interval()`, `create_time()`
   - Conversion traits between `CodecPublish` and `Publish`

5. **Affected Components**:
   - All bridge plugins (Kafka, NATS, ReductStore, Pulsar, MQTT)
   - HTTP API plugin
   - Message storage systems
   - System topics
   - Topic rewriting
   - Delayed publish handling
   - Session management

6. **Migration**:
   - Updated all internal usage to new type system
   - Maintained backward compatibility through conversion traits
   - Simplified timestamp handling across the codebase

Benefits:
- **Clean Architecture**: Clear separation between protocol and business logic
- **Improved Maintainability**: Each type has a single responsibility
- **Better Performance**: Reduced codec complexity
- **Enhanced Flexibility**: Broker can add metadata without affecting protocol