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.

.custom-gcl.yml

@@ -0,0 +1,11 @@
+# This file configures golangci-lint with module plugins.
+# When you run 'make lint', it will automatically build a custom golangci-lint binary
+# with all the plugins listed below.
+#
+# See: https://golangci-lint.run/plugins/module-plugins/
+version: v2.13.1
+plugins:
+  # logcheck validates structured logging calls and parameters (e.g., balanced key-value pairs)
+  - module: "sigs.k8s.io/logtools"
+    import: "sigs.k8s.io/logtools/logcheck/gclplugin"
+    version: latest