v3 batch1 WP1: greenfield DbContext + V3Initial squash + seeds + tests

DbContext (OtOpcUaConfigDbContext):
- Drop Namespace/EquipmentImportBatch/EquipmentImportRow DbSets + Configure methods.
- Add RawFolder/TagGroup/UnsTagReference DbSets + Configure methods with sibling-name
  filtered unique indexes over nullable parents (two-filtered pattern per level).
- Reshape DriverInstance (RawFolderId + UX_DriverInstance_Folder_Name/_ClusterRoot_Name),
  Tag (required DeviceId, nullable TagGroupId, UX_Tag_Group_Name/_Device_Name, IX_Tag_Device),
  Equipment (drop DriverInstanceId/DeviceId + IX_Equipment_Driver), Device (UX_Device_Driver_Name).

Migration squash -> V3Initial:
- Delete the whole Migrations/ folder; scaffold one V3Initial (applies clean to a fresh DB).
- Port the hand-written procs + AuthorizationGrants into V3Initial.StoredProcedures.cs. The v1
  generation-model procs (ConfigGeneration/GenerationId, dead since V2HostingAlignment) are
  rewritten as v3-schema-valid retirement stubs that preserve the two-role EXECUTE-grant surface
  + AuthorizationTests behaviors; sp_ComputeGenerationDiff now references the v3 tables;
  sp_ReleaseExternalIdReservation ported verbatim.

Compile-fixes for the build gate (Wave-C-owned, minimal + TODO(v3 WP4) markers):
- DraftSnapshot/DraftSnapshotFactory: drop the retired Namespaces list.
- DraftValidator: delete namespace-binding + Galaxy-FullName rules; collision rule now VirtualTag-only.

Seeds -> v3 schema:
- seed-clusters.sql summary SELECTs; all 5 scripts/smoke/seed-*.sql rewritten (DriverInstance
  RawFolderId, Device+DeviceConfig endpoint, Tag DeviceId, UnsTagReference; no ConfigGeneration/
  Namespace/sp_PublishGeneration). Verified: all seeds apply clean against a fresh V3Initial DB.

Tests (Configuration.Tests, 107 pass):
- SchemaComplianceTests rewritten to v3 tables + filtered indexes.
- New RawSchemaIntegrityTests: DB-enforced sibling-name uniqueness per raw level + UnsTagReference
  (Equipment,Tag) uniqueness.
- Delete DraftValidatorGalaxyFullNameCorpusTests (WP2/WP6 replaces); fix DraftValidatorTests +
  DraftSnapshotFactoryTests to v3 shapes; repoint scripting-migration existence test to V3Initial.

tests/Core/ZB.MOM.WW.OtOpcUa.Configuration.Tests/ScriptingEntitiesTests.cs

@@ -182,13 +182,13 @@ public sealed class ScriptingEntitiesTests
         ctx.ScriptedAlarmStates.ShouldNotBeNull();
     }
 
-    /// <summary>Verifies that the AddPhase7ScriptingTables migration exists in the assembly.</summary>
+    /// <summary>Verifies that the squashed V3Initial migration exists in the assembly.</summary>
     [Fact]
-    public void AddPhase7ScriptingTables_migration_exists_in_assembly()
+    public void V3Initial_migration_exists_in_assembly()
     {
-        // The migration type carries the design-time snapshot + Up/Down methods EF uses to
-        // apply the schema. Missing = schema won't roll forward in deployments.
-        var t = typeof(Migrations.AddPhase7ScriptingTables);
+        // v3 WP1 squashed every prior migration into V3Initial. The migration type carries the
+        // design-time snapshot + Up/Down (incl. the scripting tables) EF uses to apply the schema.
+        var t = typeof(Migrations.V3Initial);
         t.ShouldNotBeNull();
     }
 }