Replaces every stringly-typed SF Symbol name with a compile-time-checked
SFSymbol case, mirroring the L10n accessor approach. A mistyped or
OS-unavailable symbol is now a build error instead of a silently blank
glyph at runtime.
Adds the SFSafeSymbols SPM package (project.yml) and migrates all call
sites: Image(systemName:)/Label(systemImage:) -> systemSymbol, and the
five symbol-carrying view properties (AppDestination.systemSymbol,
SettingsRow.icon, AboutPoint.symbol, MethodRow.icon, PolicyOption.icon)
flipped from String to SFSymbol end to end.
Add a native SwiftUI VniDrop app (Send/Receive/Settings) talking to the
Rust core via generated UniFFI Swift bindings, plus the uniffi-bindgen
helper crate. iOS uses a TabView, macOS a NavigationSplitView sidebar.
