feat(12.1-01): declared bulk actions on admin lists

- pact.HasAdminBulkActions with AdminBulkAction, its input and result
- config_list.yaml bulkActions, compiled fail-loud, needs showCheckboxes
- POST .../{controller}/bulk/{action}: ids resolved and locked through the
  list scope in one transaction; partial selection is 409
- list schema offers declared actions per principal, with confirm text
- admin SPA bulk actions menu with confirm, busy state and failure toasts
- acme.roster fixture, tracer test, OpenAPI, TS types, dist, READMEs, docs

modules/cabana/README.md

@@ -17,6 +17,7 @@ Schema-driven admin backend that compiles WinterCMS-style YAML list, form, filte
 - Form widgets and controller actions: a `type: widget` field in `fields.yaml` names a plugin custom element (`widget:`, which must start with the owning plugin's `{vendor}-{plugin}-` prefix), the controller action it runs (`action:`, registered through `pact.HasAdminActions`) and the writable scalar fields of the same form the action may write back (`fill:`). The admin SPA posts the action to a cabana-owned route, so the CSRF check, permissions (the controller's plus the action's own) and record scoping (`pact.FormExtendQuery`) never depend on plugin code; the response carries only the declared fill keys whose values encode as JSON scalars (a value whose `MarshalJSON` writes an array or object, NaN or an infinity is dropped). Like the list schema's `toolbarActions`, the form schema carries a widget field only when the requesting administrator may run its action. The field's `context` applies to the action route as it does on save: a request without `record_id` is the create form's and one with it the update form's, and a widget its context hides on that form answers 404. Unknown keys, a foreign or invalid tag, an unregistered action or a fill key that is not a writable scalar field fail boot.
 - Controller assets: a controller implementing `pact.AdminClientAssets` names JS (`.js`, `.mjs`) and CSS files under its plugin's `assets/` directory, Winter's `addJs`/`addCss`. They are read from the plugin's embedded tree at boot (a missing file fails boot; there is no disk override) and listed in the list and form schemas under `assets` as same-origin URLs with a `?v=` content hash. A form with a widget needs at least one JS file.
 - Toolbar actions: `toolbar.buttons` in `config_list.yaml` lists the built-in `create` and `delete` next to names the controller registers through `pact.HasAdminActions`. Registered actions share one namespace with widget actions, `create` and `delete` are reserved, and each toolbar action needs a label. The list schema's `toolbarActions` carries only the actions the requesting administrator may run, with localized labels; an unknown name fails boot.
+- Bulk actions: `bulkActions` in `config_list.yaml` lists names the controller registers through `pact.HasAdminBulkActions`; it needs `showCheckboxes: true`. Bulk actions have their own namespace (`create` and `delete` are reserved there too), and each needs a label. The posted ids are resolved and row-locked through `pact.ListExtendQuery` in one transaction and the action receives the loaded records, never ids: a selection that matches nothing answers `affected: 0` without running the action, and a partial match answers 409 and rolls back. The list schema's `bulkActions` carries the built-in `delete` and only the declared actions the requesting administrator may run, with localized `label` and `confirm`; an unknown or duplicate name fails boot. Each run is logged with the controller, action, administrator and affected count.
 - Server-rendered partials: `headerPartial: <name>` in `config_list.yaml` (a strip above the list) and `type: partial` with `path: <name>` in `fields.yaml` render the template `{ConfigDir}/_<name>.htm` with `html/template` against a view model from the controller's `pact.AdminPartialData`. The result reaches the SPA as an allowlisted node tree, never as an HTML string. A missing or unparsable template, a free-form path or a controller without `pact.AdminPartialData` fails boot.
 - Date pickers: a `type: datepicker` field in `fields.yaml` edits a date (`mode: date`, a `lagoon.Date` column), a date and time (`mode: datetime`, the default, a `time.Time` column stored in UTC) or a time of day (`mode: time`, a `lagoon.TimeOfDay` column); pointers to the three types make the value optional. It accepts WinterCMS's `mode`, `format` (a PHP `date()` format, served also as `displayFormat` in the SPA's tokens), `minDate`, `maxDate`, `yearRange`, `firstDay`, `twelveHour` and `ignoreTimezone`; any other key, a format letter with no equivalent, bounds on `mode: time`, `ignoreTimezone` outside `mode: datetime` or a column whose Go type does not match the mode fails boot. The save rechecks `minDate` and `maxDate` on the calendar date and answers 422 on the field. List columns take `type: date` and `type: time` for these columns; when `type` is omitted, a `time.Time` column is compiled as `datetime`, a `lagoon.Date` column as `date` and a `lagoon.TimeOfDay` column as `time`. A struct column that implements `sql.Scanner` or `driver.Valuer` is never taken for a relation.
 - File uploads: a `type: fileupload` field in `fields.yaml` edits an attachOne or attachMany relation the record model declares through `attach.HasRelations` (its `AttachRelations` method) next to `attach.Owner`. The field accepts WinterCMS's `mode` (`image` or `file`), `fileTypes`, `mimeTypes`, `maxFilesize` (megabytes), `maxFiles` (attachMany only), `imageWidth`, `imageHeight`, `thumbOptions` (only `mode`: `auto`, `exact`, `crop` or `fit`), `useCaption` and `prompt`; any other key, an image-mode file type outside jpg, jpeg, png, gif and webp, a name that is not a declared relation or a `maxFilesize` whose file plus 64 KiB of multipart framing exceeds `http.body_limits.upload_bytes` fails boot. Uploads and removals are deferred, as in WinterCMS: the SPA sends a random form session key in the `X-Session-Key` header (`cabana.SessionKeyHeader`) with every file call and with the save, the server keeps the pending work in `deferred_bindings` against that key and the signed-in administrator, and the record's next create or update save applies it inside its transaction. A retry of the same upload may send `X-Upload-Id` so the server returns the already stored file. A save that fails with 422 keeps the pending uploads; another administrator's key matches nothing. The upload route caps the request body at the smaller of `http.body_limits.upload_bytes` and `maxFilesize` plus 64 KiB and answers 413 `payload_too_large` past it; the size, type and image checks run on the server (through `attach.Store`) and answer 422 on the field. A file list (`cabana.FileItem`) carries `url` and `thumb_url` only for a public relation.
@@ -42,6 +43,7 @@ All paths are relative to `<prefix>/api/v1`. A controller ID `vendor.plugin.cont
 | GET and POST `/{vendor}/{plugin}/{controller}` | List records; create a record (needs a form and `create` in `toolbar.buttons`). |
 | GET, PUT and DELETE `/{vendor}/{plugin}/{controller}/{id}` | Show, update and delete a record (update and delete need a form). |
 | POST `/{vendor}/{plugin}/{controller}/bulk-delete` | Delete a set of records in one transaction; needs `delete` in `toolbar.buttons`. |
+| POST `/{vendor}/{plugin}/{controller}/bulk/{action}` | Run a declared bulk action on `{ids}` in one transaction; answers `{message, affected}`, 409 for a partial selection. |
 | POST `/{vendor}/{plugin}/{controller}/widgets/{field}` | Run the action of a `type: widget` field with an optional `record_id` and the fill snapshot; answers `{message, fill}`. |
 | POST `/{vendor}/{plugin}/{controller}/toolbar/{action}` | Run a registered toolbar action with an empty `{}` body; answers `{message, fill: {}}`. |
 | GET `/{vendor}/{plugin}/{controller}/partials/{name}` | Render a declared header or form partial as a node tree; `?id=` (form partials only) passes the scoped record to the view model. |
@@ -166,7 +168,10 @@ func (p *Plugin) AdminFS() fs.FS { return adminFS }
 | `cabana.ListSchema` / `cabana.FormSchema` / `cabana.RelationSchema` | Locale-neutral compiled schemas; each request works on a localized copy. |
 | `cabana.CompiledController` | One controller after compilation: list, form, relations and writable fields. |
 | `cabana.Registry` | Immutable map of compiled controllers and settings, with permission-filtered metadata. |
-| `cabana.CRUDService` | Schema-projected show, create, update, delete, bulk delete and relation options. |
+| `cabana.CRUDService` | Schema-projected show, create, update, delete, bulk delete and relation options; `cabana.CRUDService.BulkAction` runs a declared bulk action on a scoped, locked id set. |
+| `cabana.BulkAction` | One entry of a list schema's `bulkActions`: name, localized label and optional confirm text. |
+| `cabana.BulkActionResult` | Answer of the bulk action route: the localized `message` and the `affected` count. |
+| `cabana.AdminBulkAction` | Swag annotation of the bulk action route. |
 | `cabana.ExecuteList` | Runs an allowlisted, paginated list query for a controller. |
 | `cabana.RelationService` | Linked, candidate, link and unlink operations of relation managers, child create, show, update and delete (`CreateChild`, `ShowChild`, `UpdateChild`, `DeleteChildren`) and pivot values (`ShowPivot`, `UpdatePivot`); its `SessionKey` makes record id 0 the record being created in that session. |
 | `cabana.SettingsService` | Reads and transactionally updates singleton settings rows. |