Scaffold project with Kubebuilder v4

kubebuilder init --domain ryuvia.com --repo git.ryuvia.com/niklas/terdut-operator
(--license none, no per-file header boilerplate -- terdut-server's source carries
none either). Go 1.26.0/controller-runtime v0.25.0/controller-tools v0.22.0, whatever
the current kubebuilder CLI (v4.16.0) scaffolds -- not pinned back to terdut-server's
go 1.25.9, since this is a separate module with its own toolchain.

Verified locally: build, vet, fmt all clean; `make lint` (golangci-lint, fetched into
bin/) 0 issues; `make test` (controller-gen + setup-envtest, fetched into bin/,
downloads real envtest binaries from storage.googleapis.com) passes.

Dropped kubebuilder's default .github/workflows/* -- this org runs on Gitea, not
GitHub; ci.yaml (next commit) is the only CI this repo gets.

config/prometheus/monitor_tls_patch.yaml

@@ -0,0 +1,19 @@
+# Patch for Prometheus ServiceMonitor to enable secure TLS configuration
+# using certificates managed by cert-manager
+- op: replace
+  path: /spec/endpoints/0/tlsConfig
+  value:
+    # SERVICE_NAME and SERVICE_NAMESPACE will be substituted by kustomize
+    serverName: SERVICE_NAME.SERVICE_NAMESPACE.svc
+    insecureSkipVerify: false
+    ca:
+      secret:
+        name: metrics-server-cert
+        key: ca.crt
+    cert:
+      secret:
+        name: metrics-server-cert
+        key: tls.crt
+    keySecret:
+      name: metrics-server-cert
+      key: tls.key