- Add centralised qdrant_config.py helper with env-var fallback for
  QDRANT_URL, QDRANT_API_KEY, QDRANT_REPLICATION_FACTOR, QDRANT_SHARD_NUMBER
- Update all 6 Qdrant processors to use the helper; writers pass
  replication_factor and shard_number to create_collection
- Fix hardcoded Cassandra replication_factor=1 in cassandra_kg.py,
  write.py, and sparql_cassandra.py to respect CASSANDRA_REPLICATION_FACTOR
- Upgrade Cassandra TLS from deprecated PROTOCOL_TLSv1_2 to
  ssl.create_default_context() across all connectors