Phase 1 WP-1: EF Core DbContext with Fluent API mappings for all 26 entities

ScadaLinkDbContext with 10 configuration classes (Fluent API only), initial
migration creating 25 tables, environment-aware migration helper (auto-apply
dev, validate-only prod), DesignTimeDbContextFactory, optimistic concurrency
on DeploymentRecord. 20 tests verify schema, CRUD, relationships, cascades.

src/ScadaLink.ConfigurationDatabase/Configurations/InboundApiConfiguration.cs

@@ -0,0 +1,50 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using ScadaLink.Commons.Entities.InboundApi;
+
+namespace ScadaLink.ConfigurationDatabase.Configurations;
+
+public class ApiKeyConfiguration : IEntityTypeConfiguration<ApiKey>
+{
+    public void Configure(EntityTypeBuilder<ApiKey> builder)
+    {
+        builder.HasKey(k => k.Id);
+
+        builder.Property(k => k.Name)
+            .IsRequired()
+            .HasMaxLength(200);
+
+        builder.Property(k => k.KeyValue)
+            .IsRequired()
+            .HasMaxLength(500);
+
+        builder.HasIndex(k => k.Name).IsUnique();
+        builder.HasIndex(k => k.KeyValue).IsUnique();
+    }
+}
+
+public class ApiMethodConfiguration : IEntityTypeConfiguration<ApiMethod>
+{
+    public void Configure(EntityTypeBuilder<ApiMethod> builder)
+    {
+        builder.HasKey(m => m.Id);
+
+        builder.Property(m => m.Name)
+            .IsRequired()
+            .HasMaxLength(200);
+
+        builder.Property(m => m.Script)
+            .IsRequired();
+
+        builder.Property(m => m.ApprovedApiKeyIds)
+            .HasMaxLength(4000);
+
+        builder.Property(m => m.ParameterDefinitions)
+            .HasMaxLength(4000);
+
+        builder.Property(m => m.ReturnDefinition)
+            .HasMaxLength(4000);
+
+        builder.HasIndex(m => m.Name).IsUnique();
+    }
+}