chore: add pre-commit config for local lint enforcement

Adds .pre-commit-config.yaml with:
- golangci-lint v2.1.6 with 5m timeout
- Basic file hygiene hooks (trailing whitespace, EOF fixer, YAML check)

Install with: pre-commit install

.pre-commit-config.yaml

@@ -0,0 +1,14 @@
+repos:
+  - repo: https://github.com/golangci/golangci-lint
+    rev: v2.1.6
+    hooks:
+      - id: golangci-lint
+        args: [--timeout=5m]
+
+  - 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
+      - id: check-added-large-files