feat(api): .NET 10 multi-tenant REST API

Full backend implementation:
- Multi-tenant cafe/restaurant management (menus, orders, tables, staff)
- POS order flow with ZarinPal and Snappfood payment integration
- OTP authentication via Kavenegar SMS
- QR digital menu with public discover/finder endpoints
- Customer loyalty, coupons, CRM
- PostgreSQL via EF Core, Redis for caching/sessions
- Background jobs, webhook handlers
- Full migration history

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

tests/Meezi.API.Tests/PlanLimitsTests.cs

@@ -0,0 +1,44 @@
+using Meezi.Core.Constants;
+using Meezi.Core.Enums;
+using Xunit;
+
+namespace Meezi.API.Tests;
+
+public class PlanLimitsTests
+{
+    [Theory]
+    [InlineData(PlanTier.Free, 1)]
+    [InlineData(PlanTier.Pro, 3)]
+    public void MaxBranches_MatchesTier(PlanTier tier, int expected)
+    {
+        Assert.Equal(expected, PlanLimits.MaxBranches(tier));
+    }
+
+    [Fact]
+    public void MaxBranches_Business_IsUnlimited()
+    {
+        Assert.Equal(int.MaxValue, PlanLimits.MaxBranches(PlanTier.Business));
+    }
+
+    [Theory]
+    [InlineData(PlanTier.Free, 8)]
+    [InlineData(PlanTier.Pro, 90)]
+    public void MaxReportHistoryDays_MatchesTier(PlanTier tier, int expected)
+    {
+        Assert.Equal(expected, PlanLimits.MaxReportHistoryDays(tier));
+    }
+
+    [Fact]
+    public void MaxReportHistoryDays_Business_IsUnlimited()
+    {
+        Assert.Equal(int.MaxValue, PlanLimits.MaxReportHistoryDays(PlanTier.Business));
+    }
+
+    [Theory]
+    [InlineData(PlanTier.Free, 1)]
+    [InlineData(PlanTier.Pro, 3)]
+    public void MaxTerminals_MatchesTier(PlanTier tier, int expected)
+    {
+        Assert.Equal(expected, PlanLimits.MaxTerminals(tier));
+    }
+}