Add Qdrant vector database client

[alceops]

Closes #273

Adds a Qdrant vector database client to the TypeScript package using Qdrant's REST API directly (no qdrant SDK package).

Implemented:

• QdrantClient with direct REST search, upsertPoints, and multi-embedding dbQuery helpers.
• Namespace filtering, named vector support, API key header support, payload/vector toggles, and result normalization for EdgeChains-style text/metadata fields.
• Exports from the db package.
• Jest coverage for REST request shape and multi-embedding deduplication.

Verification:

• npm run build
• npx jest src/db/src/tests/qdrant-client/qdrantClient.test.ts --runInBand

[github-actions]

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[alceops]

I have read the Arakoo CLA Document and I hereby sign the CLA

[alceops]

recheck

[alceops]

Quick status/verification note: this PR is still mergeable and all visible checks are green after the CLA recheck. Local verification from the submitted branch: npm run build passed and npx jest src/db/src/tests/qdrant-client/qdrantClient.test.ts --runInBand passed. I can turn around any requested changes quickly if helpful.