## Why

Operators need a way to remove server instances that are stuck in `running` or `installing` state when the runtime can no longer be stopped cleanly. The current delete safety rule blocks those instances forever, which leaves stale servers in the active management console.

## What Changes

- Add an explicit forced delete path to the existing server deletion flow.
- Preserve owner/platform-admin authorization and current-password confirmation for all server deletion.
- Require an additional force confirmation when deleting a running or installing instance.
- Keep deletion as a soft delete that marks the server instance `deleted` and preserves history.
- Make the UI expose forced deletion only through the existing destructive password confirmation dialog.

## Capabilities

### New Capabilities
- `server-deletion`: server instance soft deletion, including authorization, password confirmation, and explicit forced deletion of active/stuck instances.

### Modified Capabilities

## Impact

- `platform/` delete DTO, API handler docs, service validation, and tests.
- `platform_web/` delete request types, client-side delete dialog, error/confirmation copy, and tests.
- No changes to run executor ownership, plugin lifecycle execution, or hard-delete persistence.