fix(ui): F8-06 calculator polish — drop delete-class button, reserve lock slot

- Remove the `delete <ship_class_name>` button (and `deleteClass`,
  `canDelete`, `.delete` CSS, `game.calculator.action.delete` i18n key)
  from the calculator. Delete-class lives in the ship-classes table —
  the broader rework will land under #53.
- Bombing and cargo-capacity rows now reserve a hidden lock-slot
  placeholder so their value column lines up vertically with the
  mass/speed/attack/defence rows (which carry a lock button).

ui/frontend/src/lib/i18n/locales/en.ts

@@ -364,7 +364,6 @@ const en = {
 	"game.calculator.name.placeholder": "new class name",
 	"game.calculator.name.existing": "your ship classes",
 	"game.calculator.action.create": "create",
-	"game.calculator.action.delete": "delete",
 	"game.calculator.col.ship": "ship",
 	"game.calculator.col.tech": "tech",
 	"game.calculator.field.drive": "drive",