Explore how we might eventually support digital e-signatures

## Context

Improving assurance with support for e-signatures in forms is on the roadmap as an "opportunity on the radar to explore"

## User story

### Form building / Response retrieving
As a **form builder or program administrator**
I want to **include digital or e-signatures as part of my form for increased confidence**
So that **I can have official confirmation, a higher-level of assurance for important matters**

For example:

Clients have also asked about this feature at various points in time:

> https://gcdigital.slack.com/archives/C09CM76GCS0/p1788962102030129
> Wish there was a way to place some form of a digital signature directly within a GC Form instead of having to rely on attachments.

## Acceptance criteria

- [ ] Provides an accessible experience
- [ ] Provides equal service in French and English
- [ ] Provides auto-completion options for fields
- [ ] Provides clear validation feedback and error messages
- [ ] Works in unauthenticated state (signed out) and authenticated (signed in)
- [ ] Works with draft, published, open, closed, archived forms
- [ ] Works with collaboration, versioning,
- [ ] Works with older versions of forms (backwards compatibility)
- [ ] Works with email delivery, API retrieval and HTML/CSV/JSON download
- [ ] Works on Chrome, Firefox, Edge, Safari, and Opera
- [ ] Can be navigated using a screenreader
- [ ] Can be navigated using a keyboard
- [ ] Can be navigated with increased magnification
- [ ] Can be perceived with strong colour contrast
- [ ] Meets a11y testing / WCAG 2.1 AA requirements
- [ ] Meets Protected B level of security, with safeguards in place
- [ ] Mitigates or documents risks involved
- [ ] Collects monitoring data intended, updates to logs and SuperSet if needed
- [ ] Updates to marketing site, guidance pages, API docs, support canned responses, or other documentation

No implementation files, tests, or entry points are identified in the issue. Start by scoping the e-signature design against the listed form states, delivery and retrieval paths, accessibility, bilingual service, and Protected B requirements; done means an agreed, implementable scope that addresses the acceptance criteria.

Written by the indexing model from the issue text.