feat(supply-chain): energy flow estimates per chokepoint (mb/d card row) (#2780)

* feat(supply-chain): energy flow estimates per chokepoint (mb/d card row)

- Add FlowEstimate proto message + ChokepointInfo field 15; regenerate stubs
- Add baselineId mapping to _chokepoint-ids.ts (7 of 13 chokepoints)
- Add relayId to seed-chokepoint-baselines.mjs CHOKEPOINTS entries
- New seed-chokepoint-flows.mjs: reads portwatch + baselines, computes
  7d tanker avg vs 90d baseline, outputs flow_ratio and current_mbd;
  prefers DWT (capTanker) when available; flags disruption if last 3 days
  each below 0.85 threshold; writes energy:chokepoint-flows:v1 (TTL 3d)
- get-chokepoint-status.ts: parallel-reads flows key, attaches flowEstimate
- SupplyChainPanel: compact card gains mb/d row (red <85%, amber <95%)
- 19 new unit tests for flow computation and seeder contract

* fix(chokepoint-flows): base useDwt on 90d baseline window, not recent 7 days

Zero recent capTanker is the disruption signal, not a reason to fall back
to vessel counts. Switching metrics during peak disruption caused the seeder
to report a higher (less accurate) flow estimate exactly when oil-flow
collapse is most acute. useDwt is now locked to whether the baseline window
has DWT data -- stable across disruption events.

Adds regression test covering DWT-collapse scenario.

* fix(chokepoint-flows): require majority DWT coverage in baseline before activating DWT mode

capBaselineSum > 0 would activate DWT on a single non-zero day during
partial data roll-out, pulling down the baseline average via zero-filled
gaps. Now requires >= ceil(prev90.length / 2) days with DWT data.
ArcGIS data is all-or-nothing per chokepoint in practice, so this
guard catches edge cases without affecting normal operation.

proto/worldmonitor/supply_chain/v1/supply_chain_data.proto

@@ -18,6 +18,16 @@ message ShippingIndex {
   bool spike_alert = 8;
 }
 
+message FlowEstimate {
+  double current_mbd = 1;
+  double baseline_mbd = 2;
+  double flow_ratio = 3;
+  bool disrupted = 4;
+  string source = 5;
+  string hazard_alert_level = 6;
+  string hazard_alert_name = 7;
+}
+
 message ChokepointInfo {
   string id = 1;
   string name = 2;
@@ -33,6 +43,7 @@ message ChokepointInfo {
   repeated string directions = 12;
   repeated DirectionalDwt directional_dwt = 13 [deprecated = true];
   TransitSummary transit_summary = 14;
+  FlowEstimate flow_estimate = 15;
 }
 
 message DirectionalDwt {