implemented post-login splash screen with Lottie animations and integrated background data prefetching during the login transition

lib/view/login/login.dart

@@ -13,6 +13,7 @@ import '../../theming/light_app_theme.dart';
 import '../../utils/haptics.dart';
 import '../pages/settings/widgets/endpoint_picker.dart';
 import 'login_controller.dart';
+import 'post_login_splash.dart';
 import 'widgets/login_branding.dart';
 import 'widgets/login_card.dart';
 
@@ -23,73 +24,89 @@ class Login extends StatefulWidget {
   State<Login> createState() => _LoginState();
 }
 
-class _LoginState extends State<Login> {
+class _LoginState extends State<Login> with SingleTickerProviderStateMixin {
   static const _marianumRed = LightAppTheme.marianumRed;
 
   final LoginController _controller = LoginController();
+  late final AnimationController _fade = AnimationController(
+    vsync: this,
+    duration: const Duration(milliseconds: 450),
+    value: 1,
+  );
 
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
     precacheImage(const AssetImage('assets/logo/icon.png'), context);
+    unawaited(PostLoginSplash.precache());
   }
 
   @override
   void dispose() {
+    _fade.dispose();
     _controller.dispose();
     super.dispose();
   }
 
   void _onLoginSuccess() {
     Haptics.heavyAccent();
-    context.read<AccountBloc>().setStatus(AccountStatus.loggedIn);
     // Re-register the periodic refresh (cancelAll runs on logout) and kick
     // off an immediate one-off so the widget populates within seconds
     // instead of waiting up to 30 minutes for the next periodic slot.
     unawaited(WidgetBackgroundTask.initialize());
     unawaited(WidgetBackgroundTask.requestImmediateRefresh());
+    // Fade the login content out before handing over to the post-login splash.
+    // Both share the red backdrop, so this reads as one continuous transition
+    // instead of an abrupt swap.
+    _fade.reverse().whenComplete(() {
+      if (!mounted) return;
+      context.read<AccountBloc>().setStatus(AccountStatus.loggedIn);
+    });
   }
 
   @override
   Widget build(BuildContext context) => Scaffold(
     backgroundColor: _marianumRed,
-    body: SafeArea(
-      child: LayoutBuilder(
-        builder: (context, constraints) => SingleChildScrollView(
-          padding: const EdgeInsets.symmetric(horizontal: 24),
-          child: Center(
-            child: ConstrainedBox(
-              constraints: BoxConstraints(
-                minHeight: constraints.maxHeight,
-                maxWidth: 420,
-              ),
-              // spaceBetween statt Spacer-in-IntrinsicHeight: bei jeder
-              // Inhaltsänderung im unteren Block (z.B. EndpointLink mit
-              // dynamischem Label) würde IntrinsicHeight sonst die Column
-              // an die intrinsic-Höhe pinnen und ein paar Pixel Overflow
-              // produzieren. spaceBetween fügt nur den verbleibenden Gap
-              // ein und schrumpft sauber auf 0, wenn der Inhalt zu hoch
-              // wird — dann übernimmt der äußere ScrollView.
-              child: Column(
-                mainAxisAlignment: MainAxisAlignment.spaceBetween,
-                children: [
-                  Column(
-                    children: [
-                      const LoginHeader(),
-                      const SizedBox(height: 28),
-                      LoginCard(
-                        controller: _controller,
-                        onSuccess: _onLoginSuccess,
-                      ),
-                      const SizedBox(height: 18),
-                      const LoginDisclaimer(),
-                    ],
-                  ),
-                  const Column(
-                    mainAxisSize: MainAxisSize.min,
-                    children: [_EndpointLink(), LoginFooter()],
-                  ),
-                ],
+    body: FadeTransition(
+      opacity: _fade,
+      child: SafeArea(
+        child: LayoutBuilder(
+          builder: (context, constraints) => SingleChildScrollView(
+            padding: const EdgeInsets.symmetric(horizontal: 24),
+            child: Center(
+              child: ConstrainedBox(
+                constraints: BoxConstraints(
+                  minHeight: constraints.maxHeight,
+                  maxWidth: 420,
+                ),
+                // spaceBetween statt Spacer-in-IntrinsicHeight: bei jeder
+                // Inhaltsänderung im unteren Block (z.B. EndpointLink mit
+                // dynamischem Label) würde IntrinsicHeight sonst die Column
+                // an die intrinsic-Höhe pinnen und ein paar Pixel Overflow
+                // produzieren. spaceBetween fügt nur den verbleibenden Gap
+                // ein und schrumpft sauber auf 0, wenn der Inhalt zu hoch
+                // wird — dann übernimmt der äußere ScrollView.
+                child: Column(
+                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
+                  children: [
+                    Column(
+                      children: [
+                        const LoginHeader(),
+                        const SizedBox(height: 28),
+                        LoginCard(
+                          controller: _controller,
+                          onSuccess: _onLoginSuccess,
+                        ),
+                        const SizedBox(height: 18),
+                        const LoginDisclaimer(),
+                      ],
+                    ),
+                    const Column(
+                      mainAxisSize: MainAxisSize.min,
+                      children: [_EndpointLink(), LoginFooter()],
+                    ),
+                  ],
+                ),
               ),
             ),
           ),

lib/view/login/post_login_splash.dart

@@ -0,0 +1,168 @@
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+import 'package:lottie/lottie.dart';
+
+import '../../theming/app_theme.dart';
+import '../../theming/light_app_theme.dart';
+
+class PostLoginSplash extends StatefulWidget {
+  const PostLoginSplash({super.key, required this.onComplete});
+
+  static const String _darkAsset = 'assets/logo/logo-anim-white.json';
+  static const String _lightAsset = 'assets/logo/logo-anim-red.json';
+
+  static LottieComposition? _darkComposition;
+  static LottieComposition? _lightComposition;
+
+  static Future<void> precache() async {
+    try {
+      _darkComposition ??= await AssetLottie(_darkAsset).load();
+      _lightComposition ??= await AssetLottie(_lightAsset).load();
+    } catch (_) {}
+  }
+
+  final VoidCallback onComplete;
+
+  @override
+  State<PostLoginSplash> createState() => _PostLoginSplashState();
+}
+
+class _PostLoginSplashState extends State<PostLoginSplash>
+    with TickerProviderStateMixin {
+  static const Duration _holdAfterLogo = Duration(milliseconds: 450);
+
+  late final AnimationController _intro;
+  late final AnimationController _outro;
+  late final AnimationController _logo;
+  late final Animation<double> _introCurve;
+  late final Animation<double> _outroCurve;
+  Timer? _safety;
+  Timer? _hold;
+
+  LottieComposition? _composition;
+  bool _started = false;
+  bool _outroStarted = false;
+  bool _completed = false;
+
+  @override
+  void initState() {
+    super.initState();
+    _intro = AnimationController(
+      vsync: this,
+      duration: const Duration(milliseconds: 900),
+    );
+    _outro = AnimationController(
+      vsync: this,
+      duration: const Duration(milliseconds: 850),
+    );
+    _introCurve = CurvedAnimation(parent: _intro, curve: Curves.easeInOut);
+    _outroCurve = CurvedAnimation(parent: _outro, curve: Curves.easeInOutCubic);
+    _logo = AnimationController(vsync: this);
+    _logo.addStatusListener((status) {
+      if (status == AnimationStatus.completed) _scheduleOutro();
+    });
+    _safety = Timer(const Duration(seconds: 6), _startOutro);
+  }
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    if (_started || _outroStarted) return;
+    final isDark = AppTheme.isDarkMode(context);
+    final cached = isDark
+        ? PostLoginSplash._darkComposition
+        : PostLoginSplash._lightComposition;
+    if (cached != null) {
+      _begin(cached);
+      return;
+    }
+    final asset = isDark
+        ? PostLoginSplash._darkAsset
+        : PostLoginSplash._lightAsset;
+    AssetLottie(asset)
+        .load()
+        .then((c) {
+          if (mounted) _begin(c);
+        })
+        .catchError((_) {});
+  }
+
+  void _begin(LottieComposition composition) {
+    if (_started || _outroStarted || !mounted) return;
+    _started = true;
+    _logo.duration = composition.duration * 0.9;
+    setState(() => _composition = composition);
+    _intro.forward(from: 0);
+    _logo.forward(from: 0);
+  }
+
+  void _scheduleOutro() {
+    if (_outroStarted || _hold != null) return;
+    _hold = Timer(_holdAfterLogo, _startOutro);
+  }
+
+  void _startOutro() {
+    if (_outroStarted) return;
+    _outroStarted = true;
+    _safety?.cancel();
+    _hold?.cancel();
+    _outro.forward().whenComplete(() {
+      if (_completed || !mounted) return;
+      _completed = true;
+      widget.onComplete();
+    });
+  }
+
+  @override
+  void dispose() {
+    _safety?.cancel();
+    _hold?.cancel();
+    _intro.dispose();
+    _outro.dispose();
+    _logo.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final surface = Theme.of(context).scaffoldBackgroundColor;
+    return AbsorbPointer(
+      child: AnimatedBuilder(
+        animation: Listenable.merge([_introCurve, _outroCurve]),
+        builder: (context, _) {
+          final intro = _introCurve.value;
+          final outro = _outroCurve.value;
+          final background = Color.lerp(
+            LightAppTheme.marianumRed,
+            surface,
+            intro,
+          );
+          return Opacity(
+            opacity: 1 - outro,
+            child: ColoredBox(
+              color: background ?? surface,
+              child: Center(
+                child: _composition == null
+                    ? const SizedBox.shrink()
+                    : Opacity(
+                        opacity: intro,
+                        child: Transform.scale(
+                          scale: (0.94 + 0.06 * intro) * (1 + 0.05 * outro),
+                          child: Lottie(
+                            composition: _composition,
+                            controller: _logo,
+                            width: 220,
+                            height: 220,
+                            fit: BoxFit.contain,
+                          ),
+                        ),
+                      ),
+              ),
+            ),
+          );
+        },
+      ),
+    );
+  }
+}