feat(support): include classic ref-code relationships in recommendation network graph

[Blume1977]

Problem

The compliance recommendation network graph (getRecommendationGraph) and the recommendation panel read only the Recommendation table. The classic ref-code relationship (user.usedRef → user.ref) is invisible there, even though it:

• drives AML (InvalidKycStatusRefUser is evaluated against getRefUser(user.usedRef)), and
• drives ref rewards.

This is not an edge case: ~14,997 userDatas have a real usedRef, of which ~92% have no Recommendation row. A user onboarded via a ref code therefore appears as an isolated node in the network even when AML flags the referral.

Concrete example

userData 330009 used ref code 171-364 (owner: userData 321067, kycStatus = Check) → AML flagged InvalidKycStatusRefUser, but the network graph showed 330009 isolated. The referrer 321067 itself reaches 47 ref-code children but only 13 show up in the graph today (recommendation rows only).

Change

• Traverse user.usedRef in both directions during the graph BFS (up via getRefUsersByRefs, down via new getUsersByUsedRefs).
• Emit ref-code edges with kind: UsedRef and the refCode; dedupe against recommendation edges per directed userData pair (confirmed recommendations also write usedRef, so recommendation wins to avoid double edges).
• Keep the global MAX_NODES = 500 safety cap; full expansion within it.
• Expose refUserDataId on user support info so the panel can link to the referrer.
• Index user.usedRef (migration) for the reverse lookup.

Verification

Validated against production data via the debug endpoint:

• 321067 dedup math: 13 recommendation + 47 ref-code children, 12 overlapping → 48 distinct children, no doubled edges, 330009 included as a ref-code edge.

Notes

• DTO change is additive (kind, refCode, refUserDataId; method/type/created made optional). Frontend counterpart: feat(compliance): show ref-code referrer in recommendation panel and network graph services#1122 (pair PR).
• No existing support.service test harness (the original graph feature shipped without one); relied on live data verification.

PR Completeness

• Migration (index on user.usedRef)
• Service/DTO updates
• Frontend synchronization (paired services PR)

[github-actions]

⚠️ Unverified Commits (1)

The following commits are not signed/verified:

• 3d21621 feat(support): include classic ref-code relationships in recommendation network graph (Blume1977)

How to sign commits

# SSH signing (recommended)
git config --global gpg.format ssh
git config --global user.signingkey ~/.ssh/id_ed25519.pub
git config --global commit.gpgsign true

# Re-sign last commit
git commit --amend -S --no-edit
git push --force-with-lease

[TaprootFreak]

Superseded by #3948, which consolidates this work into a single PR per repo (per maintainer request). #3948 contains the classic ref-code edges from here plus the recommendation-graph edge-cap fix, the lazy 1-hop neighbor expansion (replacing the full-network load), and 100% unit-test coverage of the new endpoints/helpers. Closing in favor of #3948.