Build exchange workspace and shared transaction services (#28)

frontend/app/lib/workspace/shell.dart

@@ -0,0 +1,134 @@
+import 'package:flutter/material.dart';
+
+import 'package:go_router/go_router.dart';
+
+import 'package:provider/provider.dart';
+
+import 'package:sxchnge_wallet/sxchnge_wallet.dart';
+
+import '../auth/brand_panel.dart';
+import '../providers/locale.dart';
+
+import '../generated/i18n/app_localizations.dart';
+
+class WorkspaceShell extends StatefulWidget {
+  const WorkspaceShell({super.key, required this.child, required this.path});
+  final Widget child;
+  final String path;
+  @override
+  State<WorkspaceShell> createState() => _WorkspaceShellState();
+}
+
+class _WorkspaceShellState extends State<WorkspaceShell> {
+  @override
+  void initState() {
+    super.initState();
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      if (!mounted) return;
+      final wallet = context.read<WalletProvider>();
+      if (wallet.data == null) wallet.refresh();
+      context.read<LocaleProvider>().loadAccount(wallet);
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final l = AppLocalizations.of(context)!;
+    final t = Theme.of(context);
+    final c = t.colorScheme;
+    final paths = ['/accounts', '/activity', '/limits', '/settings'];
+    final labels = [l.wAccounts, l.wActivity, l.wLimits, l.wSettings];
+    final icons = [
+      Icons.account_balance_wallet_outlined,
+      Icons.receipt_long_outlined,
+      Icons.speed_outlined,
+      Icons.tune_rounded,
+    ];
+    final index = widget.path.startsWith('/activity')
+        ? 1
+        : widget.path.startsWith('/limits') ||
+              widget.path.startsWith('/identity')
+        ? 2
+        : widget.path.startsWith('/settings')
+        ? 3
+        : 0;
+    void navigate(int i) {
+      if (['/top-up', '/exchange', '/payout'].contains(widget.path) && i >= 2) {
+        context.push(paths[i]);
+      } else {
+        context.go(paths[i]);
+      }
+    }
+
+    final wide = MediaQuery.sizeOf(context).width >= 900;
+    final content = Column(
+      children: [
+        Padding(
+          padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 12),
+          child: Column(
+            crossAxisAlignment: wide
+                ? CrossAxisAlignment.end
+                : CrossAxisAlignment.start,
+            children: [
+              if (!wide) ...[const BrandWordmark(), const SizedBox(height: 8)],
+              Text(l.wDemo, style: t.textTheme.bodySmall),
+            ],
+          ),
+        ),
+        Expanded(child: widget.child),
+      ],
+    );
+    return Scaffold(
+      body: SafeArea(
+        child: Row(
+          children: [
+            if (wide)
+              Container(
+                width: 220,
+                padding: const EdgeInsets.all(20),
+                decoration: BoxDecoration(
+                  color: c.surfaceContainerLow,
+                  border: Border(right: BorderSide(color: c.outlineVariant)),
+                ),
+                child: Column(
+                  crossAxisAlignment: CrossAxisAlignment.stretch,
+                  children: [
+                    const Padding(
+                      padding: EdgeInsets.symmetric(vertical: 24),
+                      child: BrandWordmark(),
+                    ),
+                    const SizedBox(height: 48),
+                    for (var i = 0; i < 4; i++)
+                      Padding(
+                        padding: const EdgeInsets.only(bottom: 12),
+                        child: ListTile(
+                          shape: RoundedRectangleBorder(
+                            borderRadius: BorderRadius.circular(18),
+                          ),
+                          selected: i == index,
+                          selectedTileColor: c.primaryContainer,
+                          leading: Icon(icons[i]),
+                          title: Text(labels[i]),
+                          onTap: () => navigate(i),
+                        ),
+                      ),
+                  ],
+                ),
+              ),
+            Expanded(child: content),
+          ],
+        ),
+      ),
+      bottomNavigationBar: wide
+          ? null
+          : NavigationBar(
+              selectedIndex: index,
+              onDestinationSelected: navigate,
+              destinations: [
+                for (var i = 0; i < 4; i++)
+                  NavigationDestination(icon: Icon(icons[i]), label: labels[i]),
+              ],
+            ),
+    );
+  }
+}