fix: correct configuration key from 'linters-settings' to 'settings' in golangci-lint files

backend/.golangci-fast.yml

@@ -12,7 +12,7 @@ linters:
     - ineffassign  # Ineffectual assignments
     - unused       # Unused code detection
     - gosec        # Security checks (critical issues only)
-  linters-settings:
+  settings:
     govet:
       enable:
         - shadow

backend/.golangci.yml

@@ -1,5 +1,5 @@
 # golangci-lint configuration
-version: 2
+version: "2"
 run:
   timeout: 5m
   tests: true
@@ -14,7 +14,7 @@ linters:
     - staticcheck
     - unused
     - errcheck
-  linters-settings:
+  settings:
     gocritic:
       enabled-tags:
         - diagnostic