feat: move inventory to own view model, add signing keys

lib/app/app.dart

@@ -17,7 +17,9 @@ class _KoolTabAppState extends State<KoolTabApp> {
   void initState() {
     super.initState();
 
-    _checkForUpdates();
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      _checkForUpdates();
+    });
   }
 
   Future<void> _checkForUpdates() async {
@@ -27,19 +29,92 @@ class _KoolTabAppState extends State<KoolTabApp> {
       final update = await updater.checkForUpdate();
 
       if (update == null) {
-        debugPrint("No update available: ");
+        debugPrint("No update available");
         return;
       }
 
       debugPrint("Update available: ${update.version}");
 
-      // TODO:
-      // Show update dialog here
+      if (!mounted) return;
+
+      _showUpdateDialog(update);
     } catch (e) {
       debugPrint("Update check failed: $e");
     }
   }
 
+  void _showUpdateDialog(UpdateInfo update) {
+    showDialog(
+      context: context,
+      barrierDismissible: !update.mandatory,
+      builder: (context) {
+        return AlertDialog(
+          title: const Text("Update available"),
+          content: Column(
+            mainAxisSize: MainAxisSize.min,
+            crossAxisAlignment: CrossAxisAlignment.start,
+            children: [
+              Text(
+                "Version ${update.version} is available.",
+              ),
+              const SizedBox(height: 12),
+              Text(update.notes),
+            ],
+          ),
+          actions: [
+            if (!update.mandatory)
+              TextButton(
+                onPressed: () {
+                  Navigator.pop(context);
+                },
+                child: const Text("Later"),
+              ),
+
+            FilledButton(
+              onPressed: () async {
+                Navigator.pop(context);
+
+                await _downloadAndInstall(update);
+              },
+              child: const Text("Update"),
+            ),
+          ],
+        );
+      },
+    );
+  }
+
+  Future<void> _downloadAndInstall(UpdateInfo update) async {
+    final updater = AppUpdateUtil(
+      serverUrl: "http://localhost:3000",
+    );
+
+    try {
+      final apk = await updater.downloadApk(
+        update,
+        onProgress: (progress) {
+          debugPrint(
+            "Download ${(progress * 100).toStringAsFixed(0)}%",
+          );
+        },
+      );
+
+      final valid = await updater.verifySha256(
+        apk,
+        update.sha256,
+      );
+
+      if (!valid) {
+        throw Exception("Invalid update file");
+      }
+
+      await updater.installApk(apk);
+
+    } catch (e) {
+      debugPrint("Update failed: $e");
+    }
+  }
+
   @override
   Widget build(BuildContext context) {
     return MaterialApp.router(