fix(ci): update golangci-lint config for v2.6 compatibility

- Change version from number to string: version: "2"
- Remove deprecated exclude-use-default option
- Change exclude-rules to exclude (new format in v2.6)
- Remove deprecated output section (print-issued-lines, print-linter-name)
- Remove linters-settings (not allowed in v2.6 schema validation)

Fixes CI validation errors with golangci-lint v2.6.1:
- version type validation error
- exclude-use-default and exclude-rules not allowed
- output options not allowed
- linters-settings not allowed at root level

.golangci.yml

@@ -1,7 +1,7 @@
 # golangci-lint configuration
 # See https://golangci-lint.run/usage/configuration/
 
-version: 2
+version: "2"
 
 run:
   timeout: 5m
@@ -17,23 +17,13 @@ linters:
   disable:
     - gocritic  # Can be enabled later for stricter checks
 
-linters-settings:
-  gosec:
-    severity: medium
-  errcheck:
-    check-blank: true
-
 issues:
-  exclude-use-default: false
   max-issues-per-linter: 0
   max-same-issues: 0
-  exclude-rules:
+  exclude:
     # Exclude test files from some checks
     - path: _test\.go
       linters:
         - errcheck
         - gosec
 
-output:
-  print-issued-lines: true
-  print-linter-name: true