[FormField]: Deprecate community FormField, add missing Accordion child markers

Problem

Some community components are missing deprecation markers even though a TEDI-Ready replacement exists:

FormField is not deprecated at all, although TEDI-Ready FormField exists.
Accordion children are publicly exported but have no @deprecated JSDoc, although the parent tedi-accordion is deprecated. Card and Tabs children already have it.

Community component	Selector	JSDoc `@deprecated`	Runtime warning	Storybook `deprecated` status
`FormFieldComponent`	`tedi-form-field`	❌	❌	❌
`AccordionItemComponent`	`tedi-accordion-item`	❌	–	–
`AccordionItemHeaderComponent`	`tedi-accordion-item-header`	❌	–	–
`AccordionItemContentComponent`	`tedi-accordion-item-content`	❌	–	–
`AccordionIconComponent`	`tedi-accordion-icon`	❌	–	–

Deprecating FormField starts the 6 + 3 month window from ADR-004, giving teams time to migrate.

FormField:

@deprecated JSDoc pointing to TEDI-Ready FormField
warnDeprecated("Community tedi-form-field", …) as the first statement in the constructor
Storybook status ["existsInTediReady", "deprecated"] on Community/Form/FormField

Accordion children:

@deprecated JSDoc on each class, pointing to the matching TEDI-Ready Accordion part
No runtime warning: they only work inside the deprecated tedi-accordion, which already warns
No behaviour or style changes