feat(scenarios): add step title, scenario credentials, and environment context in executor

- add nullable title column to scenario steps; exposed in create/edit forms and step table
- add scenario-credential join (many-to-many with CredentialEntity) with CRUD endpoints
- expose environment URLs in code executor helpers via helpers.env and helpers.getEnvUrl()
- resolve and cache environment per run from the login step's environmentName in scheduler
- add section spacing and step table title column to ScenarioDetailPage

client/src/ui/index.ts

@@ -10,6 +10,9 @@ export type { BadgeProps, BadgeVariant } from './Badge/Badge';
 export { Input } from './Input/Input';
 export type { InputProps } from './Input/Input';
 
+export { Textarea } from './Textarea/Textarea';
+export type { TextareaProps } from './Textarea/Textarea';
+
 export { Select } from './Select/Select';
 export type { SelectProps, SelectOption } from './Select/Select';