feat(plans): Stage 1 — Starter tier + admin-editable limit model

Foundation for the configurable plan system (Free·Starter·Pro·Business·Enterprise).

- PlanTier: append Starter=4 (no renumber → no data migration; existing tier ints
  keep meaning). Ordering/display via PlanDefinition.SortOrder; gating uses explicit
  tier sets, never `tier >= X`.
- PlanLimits: locked 5-tier matrix — Free orders/day 50→30, tables (new) Free 6/
  Starter 15/Pro 40/∞, categories Free 3→10, menu items now unlimited, terminals/
  branches/report-history ladders incl. Starter; CRM/analytics = explicit Pro+; AI-3D
  = Business+. SMS quotas kept (Free/Starter 0, Pro 50, Business 200) until the
  pay-as-you-go credit system ships (don't break paid SMS).
- PlanLimitsData (LimitsJson shape): + MaxTables/MaxMenuCategories/MaxMenuItems/
  MaxMenuAi3dPerMonth; ForTier now derives from PlanLimits (single source of truth).

No migration. 86 tests pass. Next: S2 seed 5 plans + feature catalog (editable),
S3 wire enforcement to DB, S4 admin editor.

src/Meezi.Core/Platform/PlanLimitsData.cs

@@ -1,43 +1,37 @@
+using Meezi.Core.Constants;
+using Meezi.Core.Enums;
+
 namespace Meezi.Core.Platform;
 
+/// <summary>
+/// Serializable per-plan numeric limits, stored as PlatformPlanDefinition.LimitsJson
+/// and editable by admins. Missing fields default to "unlimited" (or 0 for opt-in
+/// quotas) so older stored JSON stays safe. Defaults come from <see cref="PlanLimits"/>.
+/// </summary>
 public class PlanLimitsData
 {
     public int MaxOrdersPerDay { get; set; } = int.MaxValue;
+    public int MaxTables { get; set; } = int.MaxValue;
     public int MaxTerminals { get; set; } = int.MaxValue;
     public int MaxCustomers { get; set; } = int.MaxValue;
-    public int MaxSmsPerMonth { get; set; } = int.MaxValue;
+    public int MaxSmsPerMonth { get; set; } = 0;
     public int MaxBranches { get; set; } = int.MaxValue;
     public int MaxReportHistoryDays { get; set; } = int.MaxValue;
+    public int MaxMenuCategories { get; set; } = int.MaxValue;
+    public int MaxMenuItems { get; set; } = int.MaxValue;
+    public int MaxMenuAi3dPerMonth { get; set; } = 0;
 
-    public static PlanLimitsData ForTier(Enums.PlanTier tier) => tier switch
+    public static PlanLimitsData ForTier(PlanTier tier) => new()
     {
-        Enums.PlanTier.Free => new PlanLimitsData
-        {
-            MaxOrdersPerDay = 50,
-            MaxTerminals = 1,
-            MaxCustomers = 50,
-            MaxSmsPerMonth = 0,
-            MaxBranches = 1,
-            MaxReportHistoryDays = 8
-        },
-        Enums.PlanTier.Pro => new PlanLimitsData
-        {
-            MaxOrdersPerDay = int.MaxValue,
-            MaxTerminals = 3,
-            MaxCustomers = int.MaxValue,
-            MaxSmsPerMonth = 50,
-            MaxBranches = 3,
-            MaxReportHistoryDays = 90
-        },
-        Enums.PlanTier.Business => new PlanLimitsData
-        {
-            MaxOrdersPerDay = int.MaxValue,
-            MaxTerminals = int.MaxValue,
-            MaxCustomers = int.MaxValue,
-            MaxSmsPerMonth = 200,
-            MaxBranches = int.MaxValue,
-            MaxReportHistoryDays = int.MaxValue
-        },
-        _ => new PlanLimitsData()
+        MaxOrdersPerDay = PlanLimits.MaxOrdersPerDay(tier),
+        MaxTables = PlanLimits.MaxTables(tier),
+        MaxTerminals = PlanLimits.MaxTerminals(tier),
+        MaxCustomers = PlanLimits.MaxCustomers(tier),
+        MaxSmsPerMonth = PlanLimits.MaxSmsPerMonth(tier),
+        MaxBranches = PlanLimits.MaxBranches(tier),
+        MaxReportHistoryDays = PlanLimits.MaxReportHistoryDays(tier),
+        MaxMenuCategories = PlanLimits.MaxMenuCategories(tier),
+        MaxMenuItems = PlanLimits.MaxMenuItems(tier),
+        MaxMenuAi3dPerMonth = PlanLimits.MaxMenuAi3dPerMonth(tier),
     };
 }