firefly-iii: Prefer running on amd64 nodes

Although Firefly III works on a Raspberry Pi, a few things are pretty
slow.  Notably, the search feature takes a really long time to return
any results, which is particularly annoying when trying to add a receipt
via the Receipts app.  Adding a node affinity rule to prefer running on
an x86_64 machine will ensure that it runs fast whenever possible, but
can fall back to running on a Rasperry Pi if necessary.

firefly-iii/kustomization.yaml

@@ -36,6 +36,16 @@ patches:
     spec:
       template:
         spec:
+          affinity:
+            nodeAffinity:
+              preferredDuringSchedulingIgnoredDuringExecution:
+              - weight: 100
+                preference:
+                  matchExpressions:
+                  - key: kubernetes.io/arch
+                    operator: In
+                    values:
+                    - amd64
           containers:
           - name: firefly-iii
             volumeMounts: