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.

.golangci.yml

@@ -0,0 +1,68 @@
+version: "2"
+run:
+  allow-parallel-runners: true
+linters:
+  default: none
+  enable:
+    - copyloopvar
+    - depguard
+    - dupl
+    - errcheck
+    - ginkgolinter
+    - goconst
+    - gocyclo
+    - govet
+    - ineffassign
+    - lll
+    - modernize
+    - misspell
+    - nakedret
+    - prealloc
+    - revive
+    - staticcheck
+    - unconvert
+    - unparam
+    - unused
+    - logcheck
+  settings:
+    custom:
+      logcheck:
+        type: "module"
+        description: Checks Go logging calls for Kubernetes logging conventions.
+    depguard:
+      rules:
+        forbid-sort-pkg:
+          deny:
+            - pkg: sort
+              desc: Should be replaced with slices package
+    revive:
+      rules:
+        - name: comment-spacings
+        - name: import-shadowing
+    modernize:
+      disable:
+        - omitzero
+  exclusions:
+    generated: lax
+    rules:
+      - linters:
+          - lll
+        path: api/*
+      - linters:
+          - dupl
+          - lll
+        path: internal/*
+    paths:
+      - third_party$
+      - builtin$
+      - examples$
+formatters:
+  enable:
+    - gofmt
+    - goimports
+  exclusions:
+    generated: lax
+    paths:
+      - third_party$
+      - builtin$
+      - examples$