fix: enforce tenant/privacy scope in remote adapters

[NeerajCodz]

Motivation

• The remote adapters (Qdrant, Neo4j, S3) were performing live reads/writes/deletes without enforcing the TenantUserScope and privacy_scope carried by the port APIs, enabling cross-tenant and out-of-scope access or deletion.
• The change aims to restore fail-closed tenant/privacy isolation at the adapter boundary while keeping behavior minimal and compatible.
• The rust-best-practices skill was used to shape a minimal, idiomatic remediation that enforces scope checks.

Description

• QdrantAdapter::search now adds a privacy_level match to the Qdrant filter and binds it to request.privacy_scope so returned vector hits are constrained by the requested privacy levels.
• Neo4jAdapter now scopes graph traversal and redaction to both tenant_id and user_id by including tenant_id in the MATCH and relationship patterns and by passing tenant_id in Cypher parameters.
• S3Adapter::tombstone_object now requires the provided object_key to start with tenants/{tenant_id}/ and returns InvalidInput if it does not, preventing cross-tenant deletions; the method now uses the tenant_id parameter rather than ignoring it.
• Minor formatting/cleanup changes were applied (reflowing a few chained calls) to keep the codebase consistent.

Testing

• Ran cargo fmt --all to apply repository formatting rules and the command completed successfully.
• Ran cargo test --lib and the test suite completed successfully (11 unit tests passed, 0 failed).

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Codex Task