fix(helm): update pod resource envelope per plan §14.8

Update resources in Helm values.yaml to match the 2 vCPU / 3.75 GB envelope:
- requests: cpu 500m (was 1000m), memory 1Gi (was 2048Mi)
- limits: cpu 2000m, memory 3584Mi (was 3840Mi)

The new limits leave headroom under the 3.75 GB node limit as specified
in plan §14.8. Config defaults were already correctly sized for the
envelope per plan §14.2 per-feature memory budget.

Closes: miroir-m9q.1

charts/miroir/values.yaml

@@ -58,10 +58,10 @@ miroir:
   resources:
     limits:
       cpu: 2000m
-      memory: 3840Mi
+      memory: 3584Mi  # 3.5 GiB (leaves headroom under 3.75 GB node limit, per §14.8)
     requests:
-      cpu: 1000m
-      memory: 2048Mi
+      cpu: 500m
+      memory: 1Gi
 
   # Pod annotations
   podAnnotations: {}