fix(transport): carry derived composition-slot templates and rebuild them through the compose flow (ScadaBridge#118)

Bundles did not record that a template was a derived slot template, so the
importer re-created every slot as a BASE template named after the slot.

- Export: TemplateDto gains an additive, null-omitted `Derivation`
  (owner path + base path by stable names); a derived template carries only
  its own rows (overrides/additions, not inherited placeholders). The closure
  pulls in each derived template's base/owner; base orders first.
  schemaVersion 1.1 -> 1.2, bundleFormatVersion stays 1.
- Import: base templates go through the ordinary passes; derived templates are
  ordered topologically (DerivedTemplatePlan; cycle / duplicate / malformed =
  preview Blocker + SemanticValidationException before anything is staged),
  their owner and base resolved by path (#100 root rule), and the slot is
  created with TemplateService.AddCompositionAsync, synced in place when it
  already exists with the same base, or deleted+recomposed when the base
  differs; own rows applied as overrides, then ResyncInheritedMembersAsync.
  Missing owner/base fails that record (BundleImportDerivedTemplateUnresolved
  audit + ImportResult warning), never creating a base in its place.
- Preview/diff: derived rows are keyed by qualified name and compared against
  the target slot at the same owner path (own rows + base), so an unchanged
  slot is Identical and a same-named base template is never matched.
- Pre-#118 bundles import exactly as before (new fixture
  pre-118-derived-plaintext.scadabundle, written by a13aabc7). The field is in
  content, pinned by the signed manifest's contentHash.

Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV

tests/ZB.MOM.WW.ScadaBridge.Transport.Tests/Serialization/ManifestBuilderTests.cs

@@ -37,7 +37,7 @@ public sealed class ManifestBuilderTests
         Assert.Equal("1.0.0", manifest.ScadaBridgeVersion);
         Assert.Equal(1, manifest.BundleFormatVersion);
         // Schema minor bumped 1.0 → 1.1; format version stays 1.
-        Assert.Equal("1.1", manifest.SchemaVersion);
+        Assert.Equal("1.2", manifest.SchemaVersion);
         Assert.Null(manifest.Encryption);
     }