chore: Flutter mobile app, CI, and dev tooling

- mobile/: Flutter/Dart merchant mobile app skeleton
- .github/: GitHub Actions CI workflows
- .dockerignore: exclude host node_modules from build context
- .cursorrules: Cursor IDE project rules
- .claude/: Claude Code project settings and launch config

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

mobile/meezi_pos/lib/features/auth/login_screen.dart

@@ -0,0 +1,42 @@
+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+
+/// Phase 1: online-only OTP login (wire Dio to /api/auth/*).
+class LoginScreen extends StatefulWidget {
+  const LoginScreen({super.key});
+
+  @override
+  State<LoginScreen> createState() => _LoginScreenState();
+}
+
+class _LoginScreenState extends State<LoginScreen> {
+  final _phone = TextEditingController(text: '09121234567');
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: SafeArea(
+        child: Padding(
+          padding: const EdgeInsets.all(24),
+          child: Column(
+            crossAxisAlignment: CrossAxisAlignment.stretch,
+            children: [
+              const Text('میزی — صندوق', style: TextStyle(fontSize: 22, fontWeight: FontWeight.bold)),
+              const SizedBox(height: 24),
+              TextField(
+                controller: _phone,
+                keyboardType: TextInputType.phone,
+                decoration: const InputDecoration(labelText: 'موبایل', border: OutlineInputBorder()),
+              ),
+              const SizedBox(height: 16),
+              FilledButton(
+                onPressed: () => context.go('/pos'),
+                child: const Text('ورود (دمو)'),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}