Add release process via goreleaser, restructure Make targets

make targets each do one thing now: lint, fmt, fmt-check, test. Use
'make check' for combined lint + fmt-check + test (the standard
pre-commit gate).

Release builds are pure-Go (CGO_ENABLED=0) cross-compiling to
linux/darwin × amd64/arm64.

.goreleaser.yaml

@@ -0,0 +1,55 @@
+version: 2
+
+project_name: vaultik
+
+before:
+  hooks:
+    - go mod tidy
+
+builds:
+  - id: vaultik
+    main: ./cmd/vaultik
+    binary: vaultik
+    env:
+      - CGO_ENABLED=0
+    goos:
+      - linux
+      - darwin
+    goarch:
+      - amd64
+      - arm64
+    ldflags:
+      - -s -w
+      - -X 'git.eeqj.de/sneak/vaultik/internal/globals.Version={{ .Version }}'
+      - -X 'git.eeqj.de/sneak/vaultik/internal/globals.Commit={{ .Commit }}'
+
+archives:
+  - id: default
+    name_template: "{{ .ProjectName }}_{{ .Version }}_{{ .Os }}_{{ .Arch }}"
+    formats:
+      - tar.gz
+    files:
+      - LICENSE
+      - README.md
+
+checksum:
+  name_template: "checksums.txt"
+  algorithm: sha256
+
+snapshot:
+  version_template: "{{ incpatch .Version }}-next"
+
+changelog:
+  sort: asc
+  use: git
+  filters:
+    exclude:
+      - "^docs:"
+      - "^test:"
+      - "^chore:"
+      - "Merge pull request"
+      - "Merge branch"
+
+release:
+  draft: true
+  prerelease: auto