feat: hybrid retrieval approach

[srini047]

Implementation:
BM42 Hybrid Retrieval with Haystack + Qdrant - Hybrid search system combining sparse (BM42) and dense (mxbai-embed-large-v1) embeddings for information retrieval on the DevRev knowledge base.

Indexing Pipeline:
DocumentCleaner → FastembedSparseDocumentEmbedder (BM42)
→ SentenceTransformersDocumentEmbedder (1024-dim)
→ DocumentWriter (Qdrant)

Retrieval Pipeline:
FastembedSparseTextEmbedder (BM42) + SentenceTransformersTextEmbedder
→ QdrantHybridRetriever (RRF fusion)

Work item: ISS-269621

[srini047]

@nimit2801 Please help with the PR description validation.

[srini047]

Please use this json for results: test_queries_results.json. Have the parquet as well.

[nimit2801]

hey @srini047

Kindly add this in your PR description: https://app.devrev.ai/devrev/works/ISS-269621

[prakhar7651]

Hey!
These are your scores.
Recall@10: 0.3188
Precision@10: 0.2598