feat: add administrator repository (#11803)

Introduces the `administrators` relational table and repository layer
for the v3 backend, unifying instance, organization, project, and
project-grant membership into a single scoped model.

Closes #10220

## Changes

- **Domain**: `Administrator` struct, `AdministratorScope` enum,
`AdministratorRepository` interface with typed CRUD, column, condition,
and change helpers. Generated enumer and GoMock.
- **Migration** (`016`): `zitadel.administrators` table with a generated
`id`, scope-alignment check constraint, cascading foreign keys, and a
child `administrator_roles` table.
- **Repository**: CTE-based role mutations (`AddRole`, `RemoveRole`,
`SetRoles`) for atomicity. Roles aggregated via `ARRAY_AGG`.
- **Projection**: Event reducers for
`member.added/changed/removed/cascade_removed` across all four admin
scopes.
- **Fixes**: `Rows.Close()` error wrapping; `TextArray` nil-safe scan +
full `pgtype` array interface; `authorization` and `projectGrant` scan
helpers fixed for `ARRAY_AGG` under `database/sql`; removed unused `ctx`
parameter from `callReduce`.

---------

Co-authored-by: Marco Ardizzone <[email protected]>

internal/database/type.go

@@ -15,6 +15,11 @@ type TextArray[T ~string] pgtype.FlatArray[T]
 
 // Scan implements the [database/sql.Scanner] interface.
 func (s *TextArray[T]) Scan(src any) error {
+	if src == nil {
+		*s = nil
+		return nil
+	}
+
 	var typedArray []string
 	err := pgtype.NewMap().SQLScanner(&typedArray).Scan(src)
 	if err != nil {
@@ -29,6 +34,46 @@ func (s *TextArray[T]) Scan(src any) error {
 	return nil
 }
 
+func (s TextArray[T]) Dimensions() []pgtype.ArrayDimension {
+	if s == nil {
+		return nil
+	}
+
+	return []pgtype.ArrayDimension{{Length: int32(len(s)), LowerBound: 1}}
+}
+
+func (s TextArray[T]) Index(i int) any {
+	return s[i]
+}
+
+func (s TextArray[T]) IndexType() any {
+	var el T
+	return el
+}
+
+func (s *TextArray[T]) SetDimensions(dimensions []pgtype.ArrayDimension) error {
+	if dimensions == nil {
+		*s = nil
+		return nil
+	}
+
+	elementCount := 1
+	for _, dimension := range dimensions {
+		elementCount *= int(dimension.Length)
+	}
+
+	*s = make(TextArray[T], elementCount)
+	return nil
+}
+
+func (s TextArray[T]) ScanIndex(i int) any {
+	return &s[i]
+}
+
+func (s TextArray[T]) ScanIndexType() any {
+	return new(T)
+}
+
 // Value implements the [database/sql/driver.Valuer] interface.
 func (s TextArray[T]) Value() (driver.Value, error) {
 	if len(s) == 0 {