chore: migrate golangci-lint config to v2

golangci-lint v2 rejects the old config format, so the pre-commit hook failed on every commit. The config now uses version 2 with the same linters and exclusions.

.golangci.yml

@@ -1,19 +1,28 @@
-run:
-  timeout: 5m
-
+version: "2"
 linters:
   enable:
     - gosec
-    - staticcheck
-
-linters-settings:
+  settings:
     gosec:
-    excludes: []
-    confidence: low
       severity: medium
-
-issues:
-  exclude-dirs:
+      confidence: low
+  exclusions:
+    generated: lax
+    presets:
+      - comments
+      - common-false-positives
+      - legacy
+      - std-error-handling
+    paths:
       - .repos
       - web
-  exclude-dirs-use-default: true
+      - third_party$
+      - builtin$
+      - examples$
+formatters:
+  exclusions:
+    generated: lax
+    paths:
+      - third_party$
+      - builtin$
+      - examples$