Remove completed legacy-migration cluster from topdata (#45)

The legacy normalize migration is done (confirmed). This deletes the dead migration path: NormalizeProject + 26 *_migrate.go files, the importLegacyItempropsRegistry cluster, loadLegacyTLK, and their tests (~7.9k lines, -33 files worth). mergeLegacyTLK moved into tlk_native.go since the live TLK compiler still uses it for base_dialog.json. make check passes.

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Reviewed-on: #45
Reviewed-by: gitea-bot <gitea-bot@noreply.git.westgate.pw>
Co-authored-by: vickydotbat <vickydotbat@tutamail.com>
Co-committed-by: vickydotbat <vickydotbat@tutamail.com>

internal/topdata/tlk_native.go

@@ -727,3 +727,36 @@ func sortedKeys[M ~map[string]V, V any](input M) []string {
 func almostEqualFloat32(a, b float32) bool {
 	return math.Abs(float64(a-b)) < 0.0001
 }
+func mergeLegacyTLK(base, override *legacyTLKData) *legacyTLKData {
+	if base == nil && override == nil {
+		return nil
+	}
+	merged := &legacyTLKData{
+		Language: "en",
+		Entries:  map[string]tlkEntryData{},
+		Lock:     map[string]int{},
+	}
+	if base != nil {
+		if base.Language != "" {
+			merged.Language = base.Language
+		}
+		for key, entry := range base.Entries {
+			merged.Entries[key] = entry
+		}
+		for key, id := range base.Lock {
+			merged.Lock[key] = id
+		}
+	}
+	if override != nil {
+		if override.Language != "" {
+			merged.Language = override.Language
+		}
+		for key, entry := range override.Entries {
+			merged.Entries[key] = entry
+		}
+		for key, id := range override.Lock {
+			merged.Lock[key] = id
+		}
+	}
+	return merged
+}