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/kustomization.yaml

@@ -0,0 +1,11 @@
+resources:
+- monitor.yaml
+
+# [PROMETHEUS-WITH-CERTS] The following patch configures the ServiceMonitor in ../prometheus
+# to securely reference certificates created and managed by cert-manager.
+# Additionally, ensure that you uncomment the [METRICS WITH CERTMANAGER] patch under config/default/kustomization.yaml
+# to mount the "metrics-server-cert" secret in the Manager Deployment.
+#patches:
+#  - path: monitor_tls_patch.yaml
+#    target:
+#      kind: ServiceMonitor

config/prometheus/monitor.yaml

@@ -0,0 +1,27 @@
+# Prometheus Monitor Service (Metrics)
+apiVersion: monitoring.coreos.com/v1
+kind: ServiceMonitor
+metadata:
+  labels:
+    control-plane: controller-manager
+    app.kubernetes.io/name: terdut-operator
+    app.kubernetes.io/managed-by: kustomize
+  name: controller-manager-metrics-monitor
+  namespace: system
+spec:
+  endpoints:
+    - path: /metrics
+      port: https # Ensure this is the name of the port that exposes HTTPS metrics
+      scheme: https
+      bearerTokenFile: /var/run/secrets/kubernetes.io/serviceaccount/token
+      tlsConfig:
+        # TODO(user): The option insecureSkipVerify: true is not recommended for production since it disables
+        # certificate verification, exposing the system to potential man-in-the-middle attacks.
+        # For production environments, it is recommended to use cert-manager for automatic TLS certificate management.
+        # To apply this configuration, enable cert-manager and use the patch located at config/prometheus/servicemonitor_tls_patch.yaml,
+        # which securely references the certificate from the 'metrics-server-cert' secret.
+        insecureSkipVerify: true
+  selector:
+    matchLabels:
+      control-plane: controller-manager
+      app.kubernetes.io/name: terdut-operator

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