These strings have 0 references in code. There is likely more, but these are the most obvious.
These is additional work that needs to be done to remove references to strings that are no longer needed, but since it involves changing code, thats left for a different commit.
Since the items removed are numerous and far apart, below is the complete list this commit removes:
AlreadyPaidHelp1
AlreadyPaidHelp2
AuthProviderHelp
ButtonCancelSub
ButtonDontCancelSub
ButtonLinkMyJellyfinAccount
ButtonRegister
ButtonRetrieveKey
ButtonSignInWithConnect
ButtonTermsOfService
DonationNextStep
DownloadFFmpeg
ErrorMessageInvalidKey
FFmpegSuggestedDownload
HeaderCancelSub
HeaderEmailAddress
HeaderOptionalLinkJellyfinAccount
HeaderSupportTheTeamHelp
HeaderSupporterBenefit
HeaderThankYou
HeaderTryJellyfinPremiere
HeaderUnlockApp
HeaderUnlockSync
HeaderWelcomeBack
LabelAlreadyCanceled
LabelAlreadyCancelled
LabelAuthProvider
LabelCancelInfo
LabelClickToCancel
LabelCurrentEmailAddress
LabelCurrentEmailAddressHelp
LabelEnterConnectUserName
LabelManagement
LabelSupporterEmailAddress
LabelSupporterKey
LabelTheseFeaturesRequireSubscriptionHelpAndTrailers
ListItemPremiereSub
MessageInvalidKey
MessageKeyEmailedTo
MessageKeyRemoved
MessageKeyUpdated
MessagePleaseAcceptTermsOfService
MessagePremiereExtendedPlans
MessagePremiereStatusClose
MessagePremiereStatusGood
MessagePremiereStatusOver
MessageSubCancelError
MessageSubCancelReqSent
MessageSureYouWishToProceed
OptionIAcceptTermsOfService
PleaseSupportOtherProduces
TabBecomeSupporter
TabBranding
TabJellyfinPremiere
TabSupporterKey
TooltipLinkedToJellyfinConnect
UnzipFFmpegFile
VersionXIsAvailableForDownload
WhenDidYouPurchaseApp
