docs(storage): add qdrant and vikingdb to vector Backend Support table

[r266-tech]

#2350 (add Qdrant vectordb support) registered qdrant in the vector backend factory (openviking/storage/vectordb_adapters/factory.py _ADAPTER_REGISTRY), and qdrant is now a valid value of VectorDBBackendConfig.backend. The canonical Backend Support table in docs/{en,zh}/concepts/05-storage.md still lists only local/http/volcengine, so the new qdrant backend is invisible to users choosing a vector backend.

This adds the qdrant row, plus the vikingdb row that was already registered (VikingDBPrivateCollectionAdapter) but never documented, so the table matches _ADAPTER_REGISTRY exactly (local, http, qdrant, volcengine, vikingdb) in both the EN and ZH docs.

[github-actions]

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🎫 Ticket compliance analysis ✅ 2350 - Fully compliant Compliant requirements: Make corresponding changes to the documentation (added qdrant and vikingdb to backend support tables)

⏱️ Estimated effort to review: 1 🔵⚪⚪⚪⚪

🏅 Score: 100

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