feat: versao do app e aviso de alpha na pagina sobre

Mostra a versao (via getVersion/package_info_plus) ao lado de um badge
alpha e um aviso de que o app ainda esta em desenvolvimento.

lib/utils/platform_infos.dart

@@ -72,13 +72,12 @@ abstract class PlatformInfos {
     final l10n = L10n.of(context);
     final theme = Theme.of(context);
     final size = MediaQuery.sizeOf(context);
+    final version = await getVersion();
+    if (!context.mounted) return;
     await m.showDialog<void>(
       context: context,
       builder: (context) => m.Dialog(
-        insetPadding: const EdgeInsets.symmetric(
+        insetPadding: const EdgeInsets.symmetric(horizontal: 24, vertical: 40),
-          horizontal: 24,
-          vertical: 40,
-        ),
         child: ConstrainedBox(
           constraints: BoxConstraints(
             maxWidth: 720,
@@ -110,13 +109,52 @@ abstract class PlatformInfos {
                             fontWeight: FontWeight.bold,
                           ),
                         ),
+                        const SizedBox(height: 12),
+                        Row(
+                          mainAxisAlignment: MainAxisAlignment.center,
+                          crossAxisAlignment: CrossAxisAlignment.center,
+                          children: [
+                            Text(
+                              l10n.versionWithNumber(version),
+                              style: theme.textTheme.bodyMedium?.copyWith(
+                                color: theme.colorScheme.onSurfaceVariant,
+                              ),
+                            ),
+                            const SizedBox(width: 8),
+                            Container(
+                              padding: const EdgeInsets.symmetric(
+                                horizontal: 8,
+                                vertical: 2,
+                              ),
+                              decoration: BoxDecoration(
+                                color: theme.colorScheme.tertiaryContainer,
+                                borderRadius: BorderRadius.circular(8),
+                              ),
+                              child: Text(
+                                'alpha',
+                                style: theme.textTheme.labelMedium?.copyWith(
+                                  color: theme.colorScheme.onTertiaryContainer,
+                                  fontWeight: FontWeight.bold,
+                                ),
+                              ),
+                            ),
+                          ],
+                        ),
+                        const SizedBox(height: 8),
+                        Text(
+                          'Esta versão ainda está em fase alpha: o '
+                          'aplicativo está em desenvolvimento e ainda pode '
+                          'apresentar erros.',
+                          textAlign: TextAlign.center,
+                          style: theme.textTheme.bodySmall?.copyWith(
+                            color: theme.colorScheme.onSurfaceVariant,
+                          ),
+                        ),
                         const SizedBox(height: 24),
                         Linkify(
                           text: aboutDescription,
                           textAlign: TextAlign.center,
-                          style: TextStyle(
+                          style: TextStyle(color: theme.colorScheme.onSurface),
-                            color: theme.colorScheme.onSurface,
-                          ),
                           options: const LinkifyOptions(humanize: false),
                           linkStyle: TextStyle(
                             color: theme.colorScheme.primary,