refine: required confirmation_email field on both student forms, StudentEmail uses it directly

- Add dedicated 'confirmation_email' (type=email, required) field
  to student form at end of submission (partage + admin).
- ThesisCreateController now validates it is present and a valid
  email; form is rejected if missing/invalid.
- Autofocus mapping for confirmation_email errors.
- StudentEmail uses confirmation_email directly (removed extractEmail
  hack that mined email from free-form contact field).

TODO.md

@@ -71,3 +71,19 @@
   - [x] Update header.php action URLs
 - [x] Commit current state
 - [ ] Test all routes (/, /search, /tfe, /repertoire, /apropos, /licence, /media, /live-reload)
+
+# Now: Confirmation email on student form submission
+- [x] Create src/StudentEmail.php — builds HTML recap email, extracts email from contact field, uses SmtpRelay to send
+- [x] Wire StudentEmail::sendConfirmation() into partage/index.php handleShareLinkSubmission() after successful thesis creation
+- [x] Pass email-sent flag via session to /partage/thanks.php
+- [x] Update partage/thanks.php — show "email sent" notice with styled green badge when confirmation was sent
+
+- [x] Add "Visiter" (👁 Visit) button to student link action row in acces-etudiante.php
+  - [x] Add link (target _blank) to /partage/<slug>
+  - [x] Add .admin-btn-visit / .admin-btn-visit:hover CSS in admin.css
+
+- [x] Add required confirmation_email field to both student forms (partage/index.php + admin/add.php)
+  - [x] New fieldset at end of form with type="email", required
+  - [x] ThesisCreateController validates confirmation_email is present and valid
+  - [x] StudentEmail uses confirmation_email directly (no more extractEmail hack)
+  - [x] Autofocus mapping added for confirmation_email validation errors