fix(ci): pin golangci-lint to v1.64.8 and add config

'version: latest' was pulling golangci-lint v2.x which requires a config
file and has breaking changes from v1.x, causing the lint job to fail
after ~20s before any code was checked.

- Pin to v1.64.8 (last stable v1 release, matches local tooling)
- Add .golangci.yml with explicit linter set (errcheck, govet,
  staticcheck, unused, ineffassign, gosimple)
- Exclude errcheck from test files to avoid noise on t.Log etc.

Co-authored-by: Ona <no-reply@ona.com>

Author: Siddhant-K-code

.github/workflows/ci.yml

@@ -39,4 +39,4 @@ jobs:
       - name: golangci-lint
         uses: golangci/golangci-lint-action@1e7e51e771db61008b38414a730f564565cf7c20 # v9.2.0
         with:
-          version: latest
+          version: v1.64.8

.golangci.yml

@@ -0,0 +1,20 @@
+linters:
+  enable:
+    - errcheck
+    - gosimple
+    - govet
+    - ineffassign
+    - staticcheck
+    - unused
+
+linters-settings:
+  errcheck:
+    check-type-assertions: false
+    check-blank: false
+
+issues:
+  exclude-rules:
+    # Test files: allow unchecked errors on t.Log, t.Error etc.
+    - path: _test\.go
+      linters:
+        - errcheck