fix(sync): constrain TDengine and IoTDB targets to append writes (#891)

## Summary

- expose append-only capability for TDengine and IoTDB targets
- constrain the delivery UI to INSERT/append and remove delete
propagation
- block mutation and delete configurations during backend preflight
- add Go and frontend regression coverage

## Verification

- Go sync capability and preflight regression tests passed
- frontend delivery and Wails DTO regression tests passed
- frontend production build passed
- Wails desktop build passed

Closes #883

internal/sync/migration_capability.go

@@ -16,6 +16,7 @@ type MigrationCapability struct {
 	SupportsAutoCreate     bool                  `json:"supportsAutoCreate"`
 	SupportsAutoAddColumns bool                  `json:"supportsAutoAddColumns"`
 	RequiresExistingTarget bool                  `json:"requiresExistingTarget"`
+	SupportsMutations      bool                  `json:"supportsMutations"`
 }
 
 // ResolveMigrationCapability returns the migration runtime's effective support
@@ -28,6 +29,12 @@ func ResolveMigrationCapability(sourceConfig connection.ConnectionConfig, target
 		TargetType:  targetType,
 		SourceModel: classifyMigrationDataModel(sourceType),
 		TargetModel: classifyMigrationDataModel(targetType),
+		// Most writable targets support the job engine's update/delete semantics.
+		// Time-series targets are deliberately narrowed below.
+		SupportsMutations: true,
+	}
+	if targetType == "tdengine" || targetType == "iotdb" {
+		capability.SupportsMutations = false
 	}
 	syncConfig := SyncConfig{
 		SourceConfig: sourceConfig,

internal/sync/migration_capability_test.go

@@ -21,6 +21,7 @@ func TestResolveMigrationCapability_MySQLToPostgresUsesFullPlanner(t *testing.T)
 		SupportsAutoCreate:     true,
 		SupportsAutoAddColumns: true,
 		RequiresExistingTarget: false,
+		SupportsMutations:      true,
 	}
 
 	if got != want {
@@ -44,6 +45,7 @@ func TestResolveMigrationCapability_PostgresToKingbaseUsesSameFamilyPlanner(t *t
 		SupportsAutoCreate:     true,
 		SupportsAutoAddColumns: true,
 		RequiresExistingTarget: false,
+		SupportsMutations:      true,
 	}
 
 	if got != want {
@@ -67,6 +69,7 @@ func TestResolveMigrationCapability_OracleToSQLServerUsesExistingTargetCompatibi
 		SupportsAutoCreate:     false,
 		SupportsAutoAddColumns: false,
 		RequiresExistingTarget: true,
+		SupportsMutations:      true,
 	}
 
 	if got != want {
@@ -90,6 +93,7 @@ func TestResolveMigrationCapability_MongoToOracleReportsPlannedNonExecutablePath
 		SupportsAutoCreate:     false,
 		SupportsAutoAddColumns: false,
 		RequiresExistingTarget: true,
+		SupportsMutations:      true,
 	}
 
 	if got != want {
@@ -113,6 +117,7 @@ func TestResolveMigrationCapability_RedisToMongoReportsFullKeyspaceBridge(t *tes
 		SupportsAutoCreate:     true,
 		SupportsAutoAddColumns: false,
 		RequiresExistingTarget: false,
+		SupportsMutations:      true,
 	}
 
 	if got != want {
@@ -136,6 +141,7 @@ func TestResolveMigrationCapability_MongoToRedisReportsFullKeyspaceBridge(t *tes
 		SupportsAutoCreate:     true,
 		SupportsAutoAddColumns: false,
 		RequiresExistingTarget: false,
+		SupportsMutations:      true,
 	}
 
 	if got != want {
@@ -159,6 +165,7 @@ func TestResolveMigrationCapability_CustomPostgresUsesResolvedDriverFamily(t *te
 		SupportsAutoCreate:     true,
 		SupportsAutoAddColumns: true,
 		RequiresExistingTarget: false,
+		SupportsMutations:      true,
 	}
 
 	if got != want {
@@ -182,6 +189,7 @@ func TestResolveMigrationCapability_KafkaToQdrantIsUnsupported(t *testing.T) {
 		SupportsAutoCreate:     false,
 		SupportsAutoAddColumns: false,
 		RequiresExistingTarget: true,
+		SupportsMutations:      true,
 	}
 
 	if got != want {
@@ -200,6 +208,20 @@ func TestResolveMigrationCapability_RedisToNonMongoTargetIsUnsupported(t *testin
 	}
 }
 
+func TestResolveMigrationCapability_TimeSeriesTargetsAreAppendOnly(t *testing.T) {
+	for _, targetType := range []string{"tdengine", "iotdb"} {
+		t.Run(targetType, func(t *testing.T) {
+			capability := ResolveMigrationCapability(
+				connection.ConnectionConfig{Type: "mysql"},
+				connection.ConnectionConfig{Type: targetType},
+			)
+			if !capability.CanExecute || capability.SupportsMutations {
+				t.Fatalf("expected %s target to be executable and append-only, got %+v", targetType, capability)
+			}
+		})
+	}
+}
+
 func TestResolveMigrationCapability_GoldenDBUsesMySQLPlannerFamily(t *testing.T) {
 	got := ResolveMigrationCapability(
 		connection.ConnectionConfig{Type: "goldendb"},