feat(core): refactor linters config and improve code quality (#119)

- [x] Reorganize golangci-lint configuration with documented disable reasons
- [x] Simplify errcheck and revive linter rules with targeted exclusions
- [x] Pre-compile regex patterns in input_validation.go for performance
- [x] Fix type assertions in memory_shard.go and resp.go with safety checks
- [x] Replace string comparison with EqualFold for case-insensitive matching
- [x] Fix loop variable captures in jwk.go and logout.go
- [x] Change high goroutine log level from Info to Debug in autocleanup.go
- [x] Replace deprecated "cancelled" spelling with "canceled" throughout
- [x] Add nolint annotations for intentional unused parameters
- [x] Improve comment formatting for deprecated functions
- [x] Fix comment spelling: "marshalling" → "marshaling"
- [x] Refactor provider warnings formatting in internal/providers/warnings.go
- [x] Simplify metrics summary building in internal/recovery/metrics.go
- [x] Pre-allocate slice in error_recovery.go GetDegradedServices
- [x] Refactor context cancellation checks in redis.go

token_manager.go

@@ -454,7 +454,6 @@ func (t *TraefikOidc) refreshToken(rw http.ResponseWriter, req *http.Request, se
 	newToken, err := t.tokenExchanger.GetNewTokenWithRefreshToken(initialRefreshToken)
 	if err != nil {
 		errMsg := err.Error()
-		//nolint:gocritic // Complex error handling with provider-specific conditions
 		if strings.Contains(errMsg, "invalid_grant") || strings.Contains(errMsg, "token expired") {
 			t.logger.Debug("Refresh token expired or revoked: %v", err)
 			// Clear all tokens and authentication state when refresh token is invalid