Fix adapter tenant and privacy isolation

[NeerajCodz]

Motivation

• Qdrant searches were not enforcing VectorSearchRequest.privacy_scope, allowing results with disallowed privacy_level to be returned.
• Neo4j adapter queries omitted or hardcoded tenant_id, which could mix graph data across tenants that share a user_id and break tenant isolation.

Description

• Qdrant: enforce the requested privacy scope by converting request.privacy_scope into a privacy_level filter and adding it as a match.any clause in the search payload (src/adapters/qdrant.rs).
• Neo4j: include tenant_id when matching endpoint nodes used by merge_edge, and when matching traversal start nodes in related_memory_ids to scope traversals to the tenant (src/adapters/neo4j.rs).
• Neo4j: constrain traversal relationships to the same tenant_id/user_id via WHERE all(rel in relationships(p) WHERE rel.tenant_id = $tenant_id AND rel.user_id = $user_id) and include tenant_id in redact_memory_edges matches and parameters to avoid cross-tenant redaction.
• Minor formatting/cleanup to align request/response call sites and JSON construction in the updated adapters.

Testing

• Ran the test suite with cargo test and all unit tests passed (11 passed; 0 failed).
• No new automated tests were added for the adapters in this change.

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Codex Task