Get Kg Node Internal

Return one node's facts + edges as the generic GraphNodeDetail.

node_id is the OPAQUE graph-contract id = kg_nodes.id (a UUID). The observation + edge stores key on that UUID DIRECTLY — entity_observations. canonical_id and kg_edges.from_node/to_node are uuid FKs to kg_nodes.id (the "canonical_id" name is a misnomer; it is the node UUID, NOT canonical_key). So NO uuid→canonical_key resolution is done — resolving to the text canonical_key would match zero rows.

Read-only, service-auth via X-Internal-Key. jeevy schema terms are folded into each fact's generic meta map — no jeevy terms leak into the contract.

FINANCIAL GATE: unit_price facts are dropped unless shop.security_class == 'financial' (the keystone gate — facts are where prices live; the topology graph endpoint carries none).