Fix MariaDB CHECK constraint quoting that crash-looped startup seeding

Three CHECK constraints shipped with PostgreSQL identifier quoting left over
from the MySQL port:

  ck_grn_config_singleton       CHECK ("ConfigId" = 1)
  ck_sales_config_singleton     CHECK ("ConfigId" = 1)
  ck_warranty_periods_months    CHECK ("Months" BETWEEN 1 AND 600)

ANSI_QUOTES is not in MariaDB's default sql_mode, so a double-quoted token is a
*string literal*, not an identifier. `"ConfigId" = 1` therefore evaluates as
`'ConfigId' = 1`; MariaDB coerces the string to a number to compare it and,
under strict mode, raises `Truncated incorrect DECIMAL value: 'ConfigId'`.

The DDL creates fine and only breaks at runtime, so this got through the
deploy and then failed every INSERT into grn_config, sales_config and
warranty_periods. That includes DataSeeder's two singleton config rows, which
run immediately after MigrateAsync() in Program.cs — so the service threw
"Database migration succeeded, but startup seeding failed" on every boot and
systemd restart-looped (counter reached 110, each restart dumping core).

Fixed in the entity configurations and repaired on existing databases by
migration 20261005190000_FixCheckConstraintQuotingForMySql, which drops and
re-adds the three constraints with backticks. The drop/add is emitted as raw
SQL rather than DropCheckConstraint because MariaDB spells the removal
DROP CONSTRAINT, not MySQL's DROP CHECK; IF EXISTS keeps it re-runnable on a
database where the broken constraint was already removed by hand.

The identical trap was swept during the port itself; these three were
reintroduced by a feature migration written afterwards.

No data cleanup is needed: the failing inserts never committed, so the
affected tables are empty.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Backend/ERPCore/Infra/Persistence/Configurations/GrnConfigConfiguration.cs

@@ -13,7 +13,7 @@ public sealed class GrnConfigConfiguration : IEntityTypeConfiguration<GrnConfig>
     public void Configure(EntityTypeBuilder<GrnConfig> builder)
     {
         builder.ToTable("grn_config", t =>
-            t.HasCheckConstraint("ck_grn_config_singleton", $"\"ConfigId\" = {GrnConfig.SingletonId}"));
+            t.HasCheckConstraint("ck_grn_config_singleton", $"`ConfigId` = {GrnConfig.SingletonId}"));
 
         builder.HasKey(c => c.ConfigId);
 

Backend/ERPCore/Infra/Persistence/Configurations/SalesConfigConfiguration.cs

@@ -13,7 +13,7 @@ public sealed class SalesConfigConfiguration : IEntityTypeConfiguration<SalesCon
     public void Configure(EntityTypeBuilder<SalesConfig> builder)
     {
         builder.ToTable("sales_config", t =>
-            t.HasCheckConstraint("ck_sales_config_singleton", $"\"ConfigId\" = {SalesConfig.SingletonId}"));
+            t.HasCheckConstraint("ck_sales_config_singleton", $"`ConfigId` = {SalesConfig.SingletonId}"));
 
         builder.HasKey(c => c.ConfigId);
 

Backend/ERPCore/Infra/Persistence/Configurations/WarrantyPeriodConfiguration.cs

@@ -11,7 +11,7 @@ public sealed class WarrantyPeriodConfiguration : IEntityTypeConfiguration<Warra
     public void Configure(EntityTypeBuilder<WarrantyPeriod> builder)
     {
         builder.ToTable("warranty_periods", t =>
-            t.HasCheckConstraint("ck_warranty_periods_months", "\"Months\" BETWEEN 1 AND 600"));
+            t.HasCheckConstraint("ck_warranty_periods_months", "`Months` BETWEEN 1 AND 600"));
         builder.HasKey(p => p.WarrantyPeriodId);
 
         builder.Property(p => p.Months).IsRequired();

Backend/ERPCore/Migrations/20261005190000_FixCheckConstraintQuotingForMySql.cs

@@ -0,0 +1,53 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ERPCore.Migrations
+{
+    /// <summary>
+    /// Repairs three CHECK constraints that were created with PostgreSQL identifier quoting
+    /// (<c>"ConfigId"</c>) left over from the MySQL port. Without ANSI_QUOTES — which is not in
+    /// MariaDB's default sql_mode — a double-quoted token is a *string literal*, so
+    /// <c>"ConfigId" = 1</c> evaluates as <c>'ConfigId' = 1</c>. MariaDB coerces the string to a
+    /// number to compare it and, under strict mode, raises
+    /// <c>Truncated incorrect DECIMAL value: 'ConfigId'</c> — which made every INSERT into
+    /// grn_config / sales_config / warranty_periods fail, including the startup seeding of the
+    /// two singleton config rows (crash-looping the service on boot).
+    /// </summary>
+    /// <remarks>
+    /// Written by hand rather than scaffolded, and the drop/add is emitted as raw SQL instead of
+    /// <c>DropCheckConstraint</c>: MariaDB spells the removal <c>DROP CONSTRAINT</c> (MySQL's
+    /// <c>DROP CHECK</c> is not a safe assumption here), and <c>IF EXISTS</c> keeps this
+    /// re-runnable on a database where the broken constraint was already removed by hand.
+    /// </remarks>
+    /// <inheritdoc />
+    public partial class FixCheckConstraintQuotingForMySql : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.Sql("ALTER TABLE `grn_config` DROP CONSTRAINT IF EXISTS `ck_grn_config_singleton`;");
+            migrationBuilder.Sql("ALTER TABLE `grn_config` ADD CONSTRAINT `ck_grn_config_singleton` CHECK (`ConfigId` = 1);");
+
+            migrationBuilder.Sql("ALTER TABLE `sales_config` DROP CONSTRAINT IF EXISTS `ck_sales_config_singleton`;");
+            migrationBuilder.Sql("ALTER TABLE `sales_config` ADD CONSTRAINT `ck_sales_config_singleton` CHECK (`ConfigId` = 1);");
+
+            migrationBuilder.Sql("ALTER TABLE `warranty_periods` DROP CONSTRAINT IF EXISTS `ck_warranty_periods_months`;");
+            migrationBuilder.Sql("ALTER TABLE `warranty_periods` ADD CONSTRAINT `ck_warranty_periods_months` CHECK (`Months` BETWEEN 1 AND 600);");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            // Restores the original (broken) expressions so the migration is a faithful inverse.
+            migrationBuilder.Sql("ALTER TABLE `grn_config` DROP CONSTRAINT IF EXISTS `ck_grn_config_singleton`;");
+            migrationBuilder.Sql("ALTER TABLE `grn_config` ADD CONSTRAINT `ck_grn_config_singleton` CHECK (\"ConfigId\" = 1);");
+
+            migrationBuilder.Sql("ALTER TABLE `sales_config` DROP CONSTRAINT IF EXISTS `ck_sales_config_singleton`;");
+            migrationBuilder.Sql("ALTER TABLE `sales_config` ADD CONSTRAINT `ck_sales_config_singleton` CHECK (\"ConfigId\" = 1);");
+
+            migrationBuilder.Sql("ALTER TABLE `warranty_periods` DROP CONSTRAINT IF EXISTS `ck_warranty_periods_months`;");
+            migrationBuilder.Sql("ALTER TABLE `warranty_periods` ADD CONSTRAINT `ck_warranty_periods_months` CHECK (\"Months\" BETWEEN 1 AND 600);");
+        }
+    }
+}

Backend/ERPCore/Migrations/ErpDbContextModelSnapshot.cs

@@ -1537,7 +1537,7 @@ namespace ERPCore.Migrations
 
                     b.ToTable("grn_config", null, t =>
                         {
-                            t.HasCheckConstraint("ck_grn_config_singleton", "\"ConfigId\" = 1");
+                            t.HasCheckConstraint("ck_grn_config_singleton", "`ConfigId` = 1");
                         });
                 });
 
@@ -4443,7 +4443,7 @@ namespace ERPCore.Migrations
 
                     b.ToTable("sales_config", null, t =>
                         {
-                            t.HasCheckConstraint("ck_sales_config_singleton", "\"ConfigId\" = 1");
+                            t.HasCheckConstraint("ck_sales_config_singleton", "`ConfigId` = 1");
                         });
                 });
 
@@ -6710,7 +6710,7 @@ namespace ERPCore.Migrations
 
                     b.ToTable("warranty_periods", null, t =>
                         {
-                            t.HasCheckConstraint("ck_warranty_periods_months", "\"Months\" BETWEEN 1 AND 600");
+                            t.HasCheckConstraint("ck_warranty_periods_months", "`Months` BETWEEN 1 AND 600");
                         });
                 });