fix(a11y): add aria-describeby and aria-invalid on error messaages

[doppiam]

PR Checklist

• My branch is up-to-date with the Upstream main branch.
• The unit tests pass locally with my changes (if applicable).
• I have added tests that prove my fix is effective or that my feature works (if applicable).
• I have added necessary documentation (if appropriate).

Short description of what this resolves:

Improves form error accessibility by exposing invalid states and associating rendered error feedback with the relevant interactive control.

Changes proposed in this Pull Request:

• fix: add aria-invalid="true" to invalid Input, TextArea and Autocomplete controls
• fix: assign stable IDs to existing validation messages and reference them via aria-describedby
• fix: preserve existing help-text and consumer-provided aria-describedby references
• test: add focused accessibility coverage and update affected Storybook snapshots

[vercel]

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