v0.6.0 — Phase β-5 Marketplace

Voller Marketplace-Flow mit TabBar und Universal-Link-Handler.
Drei Live-Decks (Geografie, English A2, Periodensystem) sind
browse-, abonnier- und lernbar.

- PublicDeckEntry/PublicDeck/PublicDeckVersion/PublicDeckOwner/
  PublicDeckDetail Codable mit snake_case
- ExploreResponse, BrowseResponse, SubscribeResponse
- MarketplaceSort-Enum (recent/popular/trending)
- CardsAPI.explore/browseMarketplace/publicDeck/subscribe/unsubscribe
- MarketplaceStore @Observable mit Explore + Browse States
- ExploreView: Featured + Trending Horizontal-Carousels, Browse-Link
- BrowseView: Searchable + Sort-Picker + List
- PublicDeckView: Header/Metadata/Subscribe — Subscribe löst Auto-Fork
  serverseitig aus, Response liefert private_deck_id, NavigationLink
  zum eigenen Deck
- PublicDeckCard + BrowseRow mit forest-Theme
- RootView: TabBar (Decks/Entdecken/Account) statt Single-View
- Universal-Link-Handler: onOpenURL + onContinueUserActivity für
  https://cardecky.mana.how/d/<slug> und cards://d/<slug>
- associated-domains: applinks:cardecky.mana.how im entitlement
- 5 neue Marketplace-Decoding-Tests (35 Total grün)

Universal-Links funktionieren erst nach AASA-Setup auf
cardecky.mana.how/.well-known/apple-app-site-association
(Web-Aufgabe, heute 404).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Sources/App/RootView.swift

@@ -1,18 +1,62 @@
 import ManaCore
 import SwiftUI
 
-/// Top-Level-Switch: Login vs Deck-Liste.
-/// Ab Phase β-3 könnte hier eine Tab-Bar entstehen (Decks / Study /
-/// Stats / Account) — für β-1 reicht der einfache Switch.
+/// Top-Level-Switch: Login vs Haupt-App. Haupt-App ist eine TabBar mit
+/// drei Tabs (Decks / Entdecken / Account).
 struct RootView: View {
     @Environment(AuthClient.self) private var auth
+    @State private var selectedTab: AppTab = .decks
+    @State private var pendingDeepLinkSlug: String?
 
     var body: some View {
         switch auth.status {
         case .signedIn:
-            DeckListView()
+            mainTabs
+                .onOpenURL { url in handle(url: url) }
+                .onContinueUserActivity(NSUserActivityTypeBrowsingWeb) { activity in
+                    if let url = activity.webpageURL { handle(url: url) }
+                }
         case .unknown, .signedOut, .signingIn, .error:
             LoginView()
         }
     }
+
+    @ViewBuilder
+    private var mainTabs: some View {
+        TabView(selection: $selectedTab) {
+            DeckListView()
+                .tabItem { Label("Decks", systemImage: "rectangle.stack") }
+                .tag(AppTab.decks)
+
+            ExploreView(deepLinkSlug: $pendingDeepLinkSlug)
+                .tabItem { Label("Entdecken", systemImage: "sparkles") }
+                .tag(AppTab.explore)
+
+            NavigationStack {
+                AccountView()
+            }
+            .tabItem { Label("Account", systemImage: "person.crop.circle") }
+            .tag(AppTab.account)
+        }
+    }
+
+    /// Universal-Link- und URL-Scheme-Handler:
+    /// - `https://cardecky.mana.how/d/<slug>` → Explore-Tab + PublicDeckView
+    /// - `cards://study/<deckId>` → später (β-6 Notifications)
+    private func handle(url: URL) {
+        Log.app.info("Open URL: \(url.absoluteString, privacy: .public)")
+        if url.host == "cardecky.mana.how" || url.scheme == "cards" {
+            let parts = url.pathComponents.filter { $0 != "/" }
+            if parts.count >= 2, parts[0] == "d" {
+                pendingDeepLinkSlug = parts[1]
+                selectedTab = .explore
+            }
+        }
+    }
+}
+
+enum AppTab: Hashable {
+    case decks
+    case explore
+    case account
 }