fix: read node certification from NodeStored event payload

[sameh-farouk]

Summary

Fixes #193 — inconsistent node certification between chain and GraphQL.

nodeStored hardcoded certification = Diy and never read the actual value from the NodeStored event payload. Since spec v107, create_node assigns certification from the farming policy (which can be Certified), but the processor ignored it.

Root cause

On-chain, _create_node sets new_node.certification = farming_policy.node_certification and emits NodeStored with the full node struct. The processor received this event but always stored Diy. No NodeCertificationSet event is emitted on node creation (never has been, in any spec version), so there was no other path to capture the initial certification.

Verification

All 26 affected devnet nodes are associated with farming policy 3 (nodeCertification: Certified), confirming the root cause.

Fix

Read certification from the NodeStored event payload for each version that includes it:

• v9: no certification field → Diy default preserved (correct)
• v28/v43: reads certificationType.__kind via parseNodeCertification
• v63/v105: reads certification.__kind via parseNodeCertification
• v118: reads certification.__kind via parseNodeCertification

This matches the pattern already used in nodeUpdated.

Regression safety

• Only one isVxx branch executes per event (mutually exclusive hash checks)
• The Diy default (line 75) is set before any version-specific block, so it's always overridden for v28+
• v9 nodes are unaffected — no certification field exists, default Diy is correct
• nodeUpdated and nodeCertificationSet handlers are unchanged
• npm run build passes

Test plan

• npm run build passes
• Re-index devnet and verify the affected nodes now show Certified

[sameh-farouk]

Tested on a test vm
19 nodes now correctly Certified, matching tfcahin:
62, 74, 75, 102, 126, 170, 173, 174, 175, 178, 180, 181, 182, 184, 186, 386, 387, 388, 389
All 32 production Certified nodes remain Certified on test (superset, no regressions).