chore: add pre-commit hooks for Go, Helm, and shell

Hooks:
- trailing-whitespace, end-of-file-fixer, check-yaml (excl. Helm templates),
  check-json, check-merge-conflict, check-added-large-files, mixed-line-ending
- go fmt, go vet (local, runs from module root)
- golangci-lint --fix (local)
- helm lint + helm unittest (runs on charts/ changes)
- shellcheck (--severity=warning) for setup scripts

Run: pre-commit install && pre-commit run --all-files

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: cloud-vinyl-bot

.pre-commit-config.yaml

@@ -0,0 +1,64 @@
+repos:
+  # General file hygiene
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v5.0.0
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+      - id: check-yaml
+        args: [--allow-multiple-documents]
+        exclude: ^charts/.*/templates/
+      - id: check-json
+      - id: check-merge-conflict
+      - id: check-added-large-files
+        args: [--maxkb=500]
+      - id: mixed-line-ending
+        args: [--fix=lf]
+
+  # Go: format + vet + lint (local hooks run from the repo root)
+  - repo: local
+    hooks:
+      - id: go-fmt
+        name: go fmt
+        language: system
+        entry: gofmt -l -w
+        types: [go]
+      - id: go-vet
+        name: go vet
+        language: system
+        entry: go vet ./...
+        types: [go]
+        pass_filenames: false
+      - id: golangci-lint
+        name: golangci-lint
+        language: system
+        entry: golangci-lint run --fix
+        types: [go]
+        pass_filenames: false
+
+  # Helm: lint the chart
+  - repo: local
+    hooks:
+      - id: helm-lint
+        name: helm lint
+        language: system
+        entry: helm lint charts/cloud-vinyl/
+        pass_filenames: false
+        files: ^charts/
+
+  # Helm: unit tests
+  - repo: local
+    hooks:
+      - id: helm-unittest
+        name: helm unittest
+        language: system
+        entry: helm unittest charts/cloud-vinyl/
+        pass_filenames: false
+        files: ^charts/
+
+  # Shell: shellcheck
+  - repo: https://github.com/shellcheck-py/shellcheck-py
+    rev: v0.10.0.1
+    hooks:
+      - id: shellcheck
+        args: [--severity=warning]