handleDeepLink
Unified handler for all Meshtastic deep links and OS intents.
This method orchestrates two distinct types of URI handling:
Navigation: First attempts to parse the URI into a typed NavKey backstack via DeepLinkRouter. If successful, navigates the user to the target screen.
Data Import: If navigation fails, falls back to legacy contact/channel parsing via dispatchMeshtasticUri. This triggers import dialogs for shared nodes or channel configurations.