feat(apple): type-safe SF Symbols via SFSafeSymbols

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.

apple/project.yml

@@ -12,6 +12,9 @@ options:
 packages:
   VnidropCore:
     path: VnidropCore
+  SFSafeSymbols:
+    url: https://github.com/SFSafeSymbols/SFSafeSymbols
+    from: "5.3.0"
 
 targets:
   VniDrop:
@@ -48,6 +51,7 @@ targets:
           CODE_SIGN_ENTITLEMENTS: VniDrop/Resources/VniDrop.entitlements
     dependencies:
       - package: VnidropCore
+      - package: SFSafeSymbols
       - sdk: SystemConfiguration.framework
       - sdk: Security.framework
       - sdk: libresolv.tbd