fix(apple): recover dropped macOS client features lost in the W7/W8 refactor

The W7/W8 client refactor (extracting FullscreenController/ApprovalRequest out of
ContentView, splitting Settings) landed the DefaultsKeys + scaffolding but dropped
the feature WIRING, which was uncommitted WIP shelved in a stash during the
16:28 clipboard/v4 reconcile. Recovered from that stash (+ its untracked-files
parent for the whole new ModifierLayout.swift) and re-ported onto the refactored
tree:

- invertScroll: applied in InputCapture.sendScroll (the one scroll sink) + Settings toggle
- modifierLayout (Cmd/Option switch): restored ModifierLayout.swift enum + KeyMaps
  .applyModifierLayout + InputCapture.emitKey wire-boundary + Settings picker
- fullscreen shortcut (Ctrl+Cmd+F): InputCapture ⌃⌘F interception + onToggleFullscreen
  + StreamView wiring + Stream-menu item (the .punktfunkToggleFullscreen sink +
  FullscreenController observer already survived on main)
- render scale: Settings picker + MatchWindowFollower renderScale/maxDimension
  application + StreamView/StreamViewIOS plumbing (RenderScale.swift already on main)

StreamCommands re-ported by hand (the stash hunk deleted the since-landed clipboard
item — kept it, added the fullscreen item alongside). Recovered ModifierLayout +
RenderScale tests. swift build green; 15 tests pass.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/apple/Sources/PunktfunkShared/ModifierLayout.swift

@@ -0,0 +1,52 @@
+// Location-based modifier mapping — which Windows VK each PHYSICAL modifier position forwards to
+// the host. A Mac keyboard's bottom row is `⌃ Control / ⌥ Option / ⌘ Command / space`; a Windows
+// keyboard's is `Ctrl / ⊞ Super / Alt / space`. So the key NEAREST the space bar is Command on a
+// Mac but Alt on Windows, and the next one out is Option on a Mac but the Windows key. A user who
+// grew up on Windows reaches for Alt where the Mac has Command; this setting lets them get that
+// muscle memory back WITHOUT relabelling keycaps — it remaps by physical position, not by a blunt
+// "swap these two VKs" that would also drag Control/Shift or lose the left/right distinction.
+//
+// The model: keep the physical detection (which side, which key) exactly as the OS reports it, and
+// swap only the Alt-vs-Super ROLE between the Option and Command keys, per side. So under `.windows`
+// the ⌘ position emits Alt (VK_L/RMENU) and the ⌥ position emits the Windows key (VK_L/RWIN), while
+// left stays left and right stays right. Control and Shift are in the same place on both keyboards,
+// so they never move. Lives in PunktfunkShared because both the Settings UI (PunktfunkClient) and
+// the wire-boundary remap (`InputCapture.applyModifierLayout`, PunktfunkKit) resolve it.
+
+import Foundation
+
+/// How the physical ⌥ Option / ⌘ Command keys map to host modifiers. The raw values are stable on
+/// disk — rename the cases freely, never the strings.
+public enum ModifierLayout: String, CaseIterable, Sendable {
+    /// Apple positions (default): ⌥ Option → Alt, ⌘ Command → Super/Windows. The current behaviour.
+    case mac
+    /// Windows positions: the key nearest the space bar (⌘ Command) → Alt, the next one (⌥ Option)
+    /// → the Windows/Super key. Side (left/right) is preserved.
+    case windows
+
+    /// User-facing label (Settings picker).
+    public var label: String {
+        switch self {
+        case .mac: return "Mac (⌥ Alt · ⌘ Super)"
+        case .windows: return "Windows (⌘ Alt · ⌥ Super)"
+        }
+    }
+
+    /// A one-line explanation for the setting's footer.
+    public var detail: String {
+        switch self {
+        case .mac:
+            return "The ⌥ Option key sends Alt and the ⌘ Command key sends the Windows key — the Apple layout."
+        case .windows:
+            return "The key nearest the space bar sends Alt and the next one sends the Windows key, matching a PC keyboard. Client shortcuts (⌘⎋ and friends) still use the physical ⌘ key."
+        }
+    }
+
+    /// The persisted layout (default `.mac` when unset).
+    public static var current: ModifierLayout {
+        guard let raw = UserDefaults.standard.string(forKey: DefaultsKey.modifierLayout) else {
+            return .mac
+        }
+        return ModifierLayout(rawValue: raw) ?? .mac
+    }
+}