Add Kafka reader/writer factory package

[Copilot]

Kafka client support was missing, preventing standardized reader/writer creation for topics and consumer groups.

• Kafka client package: Added kafka_client with ReaderConfig/WriterConfig and factory helpers that validate required brokers/topic.
• Configuration coverage: Reader supports group/partition and offsets; writer supports async/acks, batching, balancer, compression codec, and attempts.
• Docs: Updated module docs and README to list the new Kafka client.
• Tests: Added unit tests verifying validation and config propagation to kafka-go.

Example:

r := kafka_client.NewReader(kafka_client.ReaderConfig{
    Brokers: []string{"localhost:9092"},
    Topic:   "events",
    GroupID: "service-a",
})
w := kafka_client.NewWriter(kafka_client.WriterConfig{
    Brokers:      []string{"localhost:9092"},
    Topic:        "events",
    Async:        true,
    RequiredAcks: kafka.RequireAll,
})

Original prompt

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This section details on the original issue you should resolve

<issue_title>Kafka client with reader & writer</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Kafka client with reader & writer #21

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