refactor(apple): decompose ContentView (735 -> 272 lines)

Split the monolithic ContentView into focused view files — a pure structural refactor
with no behavior change (verified: builds macOS/iOS/tvOS, the test suite is green, and a
fidelity review against the original found no discrepancies):

- ContentView (272): the coordinator — owns the session model / host store / discovery,
  switches home<->session, holds the connect logic (it reads @AppStorage) + the dev
  hooks, and the stream builder (whose stable identity across awaiting-trust->streaming
  must NOT move — it stays here).
- HomeView (251): the hosts grid + navigation + toolbar + sheets + "On this network"
  discovery section + empty state.
- HostCards (158): HostCardView + DiscoveredCardView, sharing a CardMetrics struct
  (dedupes the platform-tuned sizing the two cards had copy-pasted).
- TrustCardView (80): the TOFU prompt + fingerprint formatting.
- StreamHUDView (67): the streaming overlay HUD.

State flows idiomatically: @StateObject (ContentView) -> @ObservedObject in subviews,
@State -> @Binding; the connect logic is passed as closures. Sheet placement is
preserved — the pairing/speed-test sheets stay on the outer body so they survive the
trust->home transition.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/apple/Sources/PunktfunkClient/HostCards.swift

@@ -0,0 +1,158 @@
+// The host grid's cards: a saved host (tap to connect, context menu) and an mDNS-discovered
+// host (tap to save + connect). Both share the same platform-tuned sizing.
+
+import PunktfunkKit
+import SwiftUI
+
+/// Shared host-card sizing — touch-first on iOS, compact on macOS/tvOS.
+private struct CardMetrics {
+    let iconSize: CGFloat
+    let iconBox: CGFloat
+    let cardPadding: CGFloat
+    let nameFont: Font
+
+    static var current: CardMetrics {
+        #if os(iOS)
+        CardMetrics(iconSize: 56, iconBox: 76, cardPadding: 28, nameFont: .title3.weight(.semibold))
+        #else
+        CardMetrics(iconSize: 42, iconBox: 56, cardPadding: 18, nameFont: .headline)
+        #endif
+    }
+}
+
+/// A saved host. The accent ring marks the most-recently-connected one; the context menu
+/// pairs / speed-tests / forgets / removes. Disabled while a session is busy.
+struct HostCardView: View {
+    let host: StoredHost
+    let isConnecting: Bool
+    let isMostRecent: Bool
+    let isBusy: Bool
+    let onConnect: () -> Void
+    let onPair: () -> Void
+    let onSpeedTest: () -> Void
+    let onForget: () -> Void
+    let onRemove: () -> Void
+
+    var body: some View {
+        let m = CardMetrics.current
+        return Button(action: onConnect) {
+            VStack(spacing: 10) {
+                ZStack {
+                    Image(systemName: "play.display")
+                        .font(.system(size: m.iconSize, weight: .light))
+                        .foregroundStyle(.tint)
+                        .opacity(isConnecting ? 0.3 : 1)
+                    if isConnecting {
+                        ProgressView()
+                    }
+                }
+                .frame(height: m.iconBox)
+                VStack(spacing: 2) {
+                    Text(host.displayName)
+                        .font(m.nameFont)
+                        .lineLimit(1)
+                    HStack(spacing: 4) {
+                        if host.pinnedSHA256 != nil {
+                            Image(systemName: "lock.fill")
+                                .font(.system(size: 9))
+                                .foregroundStyle(.secondary)
+                        }
+                        Text("\(host.address):\(String(host.port))")
+                            .font(.caption)
+                            .foregroundStyle(.secondary)
+                            .lineLimit(1)
+                    }
+                    if let last = host.lastConnected {
+                        Text("Connected \(last, format: .relative(presentation: .named))")
+                            .font(.caption2)
+                            .foregroundStyle(.tertiary)
+                            .lineLimit(1)
+                    }
+                }
+            }
+            .frame(maxWidth: .infinity)
+            .padding(.vertical, m.cardPadding)
+            .padding(.horizontal, 12)
+            #if !os(tvOS)
+            // tvOS: the .card button style owns platter + focus motion — extra chrome
+            // inside it mutes the grow/tilt. Material + accent ring are for pointer UIs.
+            .background(.regularMaterial, in: RoundedRectangle(cornerRadius: 14))
+            .overlay {
+                if isMostRecent {
+                    RoundedRectangle(cornerRadius: 14)
+                        .strokeBorder(Color.accentColor.opacity(0.35), lineWidth: 1.5)
+                }
+            }
+            #endif
+        }
+        #if os(tvOS)
+        .buttonStyle(.card)
+        #else
+        .buttonStyle(.plain)
+        #endif
+        .disabled(isBusy)
+        .contextMenu {
+            Button("Pair with PIN…", action: onPair)
+            Button("Test Network Speed…", action: onSpeedTest)
+            if host.pinnedSHA256 != nil {
+                Button("Forget Identity", action: onForget)
+            }
+            Button("Remove", role: .destructive, action: onRemove)
+        }
+    }
+}
+
+/// A host found on the LAN but not yet saved. A dashed ring distinguishes it from saved cards;
+/// tapping saves it and connects (or pairs, if the host requires it).
+struct DiscoveredCardView: View {
+    let discovered: DiscoveredHost
+    let isBusy: Bool
+    let onConnect: () -> Void
+
+    var body: some View {
+        let m = CardMetrics.current
+        return Button(action: onConnect) {
+            VStack(spacing: 10) {
+                Image(systemName: "play.display")
+                    .font(.system(size: m.iconSize, weight: .light))
+                    .foregroundStyle(.tint)
+                    .frame(height: m.iconBox)
+                VStack(spacing: 2) {
+                    Text(discovered.name)
+                        .font(m.nameFont)
+                        .lineLimit(1)
+                    HStack(spacing: 4) {
+                        Image(systemName: discovered.requiresPairing ? "lock.fill" : "wifi")
+                            .font(.system(size: 9))
+                            .foregroundStyle(.secondary)
+                        Text("\(discovered.host):\(String(discovered.port))")
+                            .font(.caption)
+                            .foregroundStyle(.secondary)
+                            .lineLimit(1)
+                    }
+                    Text(discovered.requiresPairing ? "Pairing required" : "Discovered")
+                        .font(.caption2)
+                        .foregroundStyle(.tertiary)
+                }
+            }
+            .frame(maxWidth: .infinity)
+            .padding(.vertical, m.cardPadding)
+            .padding(.horizontal, 12)
+            #if !os(tvOS)
+            .background(.regularMaterial, in: RoundedRectangle(cornerRadius: 14))
+            .overlay {
+                RoundedRectangle(cornerRadius: 14)
+                    .strokeBorder(
+                        Color.secondary.opacity(0.25),
+                        style: StrokeStyle(lineWidth: 1, dash: [4, 3]))
+            }
+            #endif
+        }
+        #if os(tvOS)
+        .buttonStyle(.card)
+        #else
+        .buttonStyle(.plain)
+        #endif
+        .disabled(isBusy)
+    }
+}