Boost Node

Increment a node’s relevance_score by a fixed +0.3 with clamp [0, 1.5].

Persists an audit entry to ConsolidationAudit with event_type kg.node.boosted. Idempotency is NOT enforced — each call stacks another +0.3 until the clamp is reached, by design (repeat clicks should reflect repeat intent).

Responses: 200 — {node_id, node_type, score_before, score_after, boosted_at, boosted_by} 404 — node not found in any table of the per-board graph