fix(support): drop recommendation edges pointing beyond the graph node cap

[TaprootFreak]

Problem

getRecommendationGraph caps the BFS at MAX_NODES (500). Ref-code (UsedRef) edges are already filtered to endpoints contained in visitedUsers, but recommendation edges are not. When the cap is reached, a recommendation edge can reference a node that was queued but never loaded, so the response contains edges pointing to nodes that are absent from nodes[]. The graph screen drops those edges silently and its edge counter over-reports (edges.length vs. rendered).

Fix

Apply the same visitedUsers membership guard to recommendation edges that the ref-code edges already use. Minimal, consistent with the existing pattern, no DTO/contract change.

Verification (real data, userDataId 321067)

• Before: 70 dangling recommendation edges; API edgeCount 584; frontend rendered 514.
• After: 0 dangling; edgeCount 514 == rendered edges; node cap (500), dedup, ref-code edges, panel and navigation all unchanged.
• prettier, eslint, build green.

Targets the #3897 feature branch so the fix folds into that PR.

[TaprootFreak]

Superseded by the consolidated #3948 (now targets develop and includes this fix).