Add Qdrant vector database support

[AdamLI-AU]

Summary

• Add a Qdrant vector database client to @arakoodev/edgechains.js/vector-db
• Use Qdrant's HTTP API directly without adding a Qdrant SDK dependency
• Support point upsert, vector query, point retrieval, point deletion, and payload update
• Export Qdrant from the vector-db package
• Add mocked tests for upsert, query, and delete request behavior

Verification

• ./node_modules/.bin/tsc -b
• ./node_modules/.bin/jest qdrant.test.ts --runInBand

Notes

• Uses Qdrant's current /collections/:collection_name/points/query endpoint for vector search.
• npm run build currently uses rm -rf, which does not run in Windows PowerShell before TypeScript starts; direct tsc -b passes.

Closes #273

[github-actions]

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[AdamLI-AU]

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[AdamLI-AU]

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