fix(postgres): varchar byte-vs-char mismatch — scale string lengths x4 for Postgres

src/GreenHome.Infrastructure/Data/GreenHomeDbContext.cs

@@ -38,9 +38,10 @@ public sealed class GreenHomeDbContext : DbContext
     {
         base.OnModelCreating(modelBuilder);
 
-        // Postgres: map DateTime -> "timestamp without time zone" (not timestamptz).
-        // Mirrors SQL Server's naive datetime2 — accepts any DateTime.Kind, so values
-        // copied from SQL Server (Kind=Unspecified) or written by the API won't crash.
+        // Postgres-specific mappings (SQL Server path is untouched):
+        //  1) DateTime -> "timestamp" (no tz): mirrors naive datetime2, accepts any Kind.
+        //  2) varchar: Postgres counts BYTES, SQL Server's nvarchar counts CHARACTERS.
+        //     x4 keeps char-count semantics for any UTF-8 charset (Persian = 2 bytes/char).
         if (Database.ProviderName == "Npgsql.EntityFrameworkCore.PostgreSQL")
         {
             foreach (var et in modelBuilder.Model.GetEntityTypes())
@@ -49,6 +50,8 @@ public sealed class GreenHomeDbContext : DbContext
                 {
                     if (p.ClrType == typeof(DateTime) || p.ClrType == typeof(DateTime?))
                         p.SetColumnType("timestamp");
+                    else if (p.ClrType == typeof(string) && p.GetMaxLength() is int len)
+                        p.SetColumnType($"character varying({len * 4})");
                 }
             }
         }