fix: suppress gosec G115/G118 false positive warnings

- G115 (integer overflow): Added nosec comments for safe type conversions
  where values are bounded by design (e.g., rng.Intn(255) returns 0-254)
- G118 (context.Background): Added nosec for intentional async goroutines
  that use WithTimeout for bounded execution after request completes

Note: G101 (hardcoded credentials) warnings are low-confidence false
positives - OAuth fields use getEnv() to read from environment.

internal/pkg/errors/errors.go

@@ -76,7 +76,8 @@ func (e *ApplicationError) WithMetadata(md map[string]string) *ApplicationError
 func New(code int, reason, message string) *ApplicationError {
 	return &ApplicationError{
 		Status: Status{
-			Code:    int32(code),
+			// #nosec G115 - HTTP status codes (200-599) fit safely in int32
+			Code:    int32(code), // #nosec G115
 			Message: message,
 			Reason:  reason,
 		},