[SparkyFitness] Add configurable backup barcode providers

## Is your feature request related to a problem? Please describe. When scanning a barcode, if the default provider doesn't have the product the scan fails. ## Describe the solution you'd prefer Add the ability to configure backup barcode providers in the existing barcode/provider settings. If a barcode isn't found in the default provider, SparkyFitness should automatically try each enabled backup provider one by one in the user-defined order. If a match is found, it should be used silently with no interruption to the user. ## Describe alternatives you've considered Either doing a nutritional label scan or changing default barcode providers and trying again. ## Additional context This would significantly reduce scan failures for users whose food libraries span multiple barcode databases, while keeping the experience seamless.