fix(opencost): use Hetzner pricing API values and ECB FX rate

> 🤖 Generated by the Daily AI Assistant

Replaced hand-edited assumptions with values pulled directly from the
Hetzner Cloud Pricing API (`GET /v1/pricing`, location fsn1) and the
ECB EUR→USD reference rate for 2026-05-27.

API-verified (net of VAT):
  CX33 cap = €6.49 / server / month  (hourly €0.0104)
  Volumes  = €0.0572 / GB / month
  Egress   = €1.00 / TB overage  (€0.001 / GB; 20 TiB incl. per server)

FX (ECB reference, 2026-05-27): 1.1637 EUR/USD. The previous 1.08
assumption was 8% low.

Re-derived (50/50 CPU-RAM split, unchanged convention):
  €6.49 × 1.1637 = $7.5524 / server / month
  CPU = $7.5524 × 0.5 / 4 vCPU  ≈ $0.9441 / vCPU-month  (was 0.876)
  RAM = $7.5524 × 0.5 / 8 GB    ≈ $0.4720 / GB-month    (was 0.438)
  Vol = €0.0572 × 1.1637        ≈ $0.0666 / GB-month    (was 0.0618)
  Egress = €0.001 × 1.1637      ≈ $0.001164 / GB        (was 0.001 flat)

End-to-end check (1 vCPU for 1 hour):
  ConfigMap CPU = 0.9441 → OpenCost / 730 = $0.001293 / vCPU-hour
  Real cost     = (€6.49 × 0.5 / 4 vCPU / 730 hr) × 1.1637
                =  €0.001112 × 1.1637 = $0.001294 / vCPU-hour ✓

Using net (excl. VAT) because VAT is location-dependent (DK = 25%) and
typically reclaimable for businesses; tracking it would conflate
compute cost with tax overhead. Gross is +25% on every figure.

Validated with `ksail workload validate` on both clusters/local and
clusters/prod (256 files each).

Author: devantler

k8s/bases/infrastructure/controllers/opencost/helm-release.yaml

@@ -42,42 +42,51 @@ spec:
       # Hetzner Cloud custom pricing — CX33 monthly cap decomposed into
       # per-resource-unit USD costs. CX33 spec verified live with
       # `kubectl get nodes`: 4 vCPU, 7916176 KiB RAM (8 GB nominal), 80 GB NVMe.
-      # Price source: Hetzner price-adjustment doc, effective 2026-04-01:
-      #   https://docs.hetzner.com/general/infrastructure-and-availability/price-adjustment/
-      #   CX33 cap = €6.49 / server / month  → $7.01 at EUR/USD ≈ 1.08
-      #   Volumes = €0.0572 / GB / month     → $0.0618 / GB / month
+      # Price source: Hetzner Cloud Pricing API (2026-05, location fsn1, net
+      # of VAT — gross is +25% but VAT is reclaimable / location-dependent and
+      # tracking it in OpenCost would conflate compute cost with tax overhead):
+      #   curl -H "Authorization: Bearer $HCLOUD_TOKEN" \
+      #        https://api.hetzner.cloud/v1/pricing
+      #     CX33 cap = €6.49 / server / month   (hourly €0.0104)
+      #     Volumes  = €0.0572 / GB / month
+      #     Egress   = €1.00 / TB overage  (€0.001 / GB; 20 TiB incl. per server)
+      # FX: ECB EUR→USD reference rate 2026-05-27 = 1.1637.
       #
       # IMPORTANT: OpenCost interprets CPU / spotCPU / RAM / spotRAM / GPU / storage
       # in the costModel ConfigMap as USD PER MONTH and divides by HoursPerMonth=730
       # to get an hourly rate (opencost providerconfig.go:188, customprovider.go:95).
       # Network egress fields are passed through as-is (USD per GB transferred).
       #
-      # 50/50 CPU-RAM split of the $7.01/server/month server cost (Hetzner does
-      # not publish a CPU/RAM breakdown — this is an allocation convention):
-      #   CPU: $7.01 × 0.5 / 4 vCPU ≈ $0.876 / vCPU-month
-      #   RAM: $7.01 × 0.5 / 8 GB   ≈ $0.438 / GB-month
+      # Derivation:
+      #   €6.49/server/month × 1.1637 = $7.5524/server/month
+      #   50/50 CPU-RAM split (Hetzner does not publish a breakdown — convention):
+      #     CPU: $7.5524 × 0.5 / 4 vCPU ≈ $0.9441 / vCPU-month
+      #     RAM: $7.5524 × 0.5 / 8 GB   ≈ $0.4720 / GB-month
+      #   Volume: €0.0572 × 1.1637 ≈ $0.0666 / GB-month
+      #   Egress: €0.001  × 1.1637 ≈ $0.001164 / GB
       #
       # End-to-end sanity check (1 vCPU for 1 hour):
-      #   ConfigMap CPU = 0.876 → OpenCost / 730 = $0.00120 / vCPU-hour
-      #   Real cost     = (€6.49 × 0.5 / 4 vCPU / 730 hr) × 1.08 = $0.00120 / vCPU-hour ✓
+      #   ConfigMap CPU = 0.9441 → OpenCost / 730 = $0.001293 / vCPU-hour
+      #   Real cost     = (€6.49 × 0.5 / 4 vCPU / 730 hr) × 1.1637
+      #                 =  €0.001112 × 1.1637 = $0.001294 / vCPU-hour ✓
       # https://www.opencost.io/docs/configuration/on-prem#custom-pricing-using-the-opencost-helm-chart
       customPricing:
         enabled: true
         createConfigmap: true
         provider: custom
         costModel:
-          description: "Hetzner Cloud CX33 — 4 vCPU / 8 GB / 80 GB NVMe (50/50 CPU-RAM split, USD/month)"
-          CPU: 0.876
+          description: "Hetzner Cloud CX33 — 4 vCPU / 8 GB / 80 GB NVMe (50/50 CPU-RAM split, USD/month net of VAT)"
+          CPU: 0.9441
           spotCPU: 0
-          RAM: 0.438
+          RAM: 0.4720
           spotRAM: 0
           GPU: 0
-          storage: 0.0618
+          storage: 0.0666
           # Egress: passed through as USD per GB transferred; CX33 includes
-          # 20 TB/month free, overage ≈ $0.001/GB on Hetzner Cloud.
-          zoneNetworkEgress: 0.001
-          regionNetworkEgress: 0.001
-          internetNetworkEgress: 0.001
+          # 20 TiB/month free, overage ≈ €1.00/TB = $0.001164/GB.
+          zoneNetworkEgress: 0.001164
+          regionNetworkEgress: 0.001164
+          internetNetworkEgress: 0.001164
 
       exporter:
         replicas: 1