feat: add reader vote widget and vote-service

The skills-review desk is static, so "which draft would you ship?" needs a
stateful counterpart. vote-service is a small Go API on its own pod backed by
a JSON file on a ReadWriteOnce PVC, with one active vote per skill per source
IP as the anti-abuse rule and CORS (ALLOWED_ORIGIN) as the caller boundary.

Deployment notes that differ from the obvious path, all confirmed against the
live cluster: the image is side-loaded with `ctr image import` plus
`imagePullPolicy: Never` because kubelet has no credentials for the Nexus ref;
the pod is pinned to `kubernets` because the hostpath PV takes a nodeAffinity
for whichever node first binds it; and public exposure is Caddy on the VPS,
not the cloudflared tunnel.

The ingress controller runs with `use-forwarded-headers` off, so nginx
overwrites X-Forwarded-For with its own peer — every visitor would collapse
into one voter and each skill would cap at one vote overall. Caddy stamps the
true remote address into X-Client-IP, which nginx forwards untouched, and
clientIP() reads that first. Scoped to this app rather than flipping the
global flag, which would change client-IP handling for every other ingress.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

vote-service/go.mod

@@ -0,0 +1,3 @@
+module github.com/marcospaulo/ai-for-dummies/vote-service
+
+go 1.22