Add autosave draft system for partage form with HTMX-based session persistence

- New fragment endpoint POST/GET /partage/fragments/draft.php:
  saves all form fields to PHP session, excludes file/csrf/slug fields
  GET returns JSON for JS hydration on page load
  rotates both global CSRF and share CSRF tokens in sync

- form.php accepts optional $formExtraAttrs and $showAutosaveStatus:
  allows injecting HTMX attributes and 'Brouillon enregistré' indicator

- renderShareLinkForm adds hx-post with change/input debounce trigger,
  loads autosave-handler.js, hydrate fields from draft on page load

- Draft cleared on successful form submission in handleShareLinkSubmission

- autosave-handler.js now also updates share_link_token hidden input
  when rotating CSRF token (partage form uses both csrf_token and share_link_token)

- Added .autosave-status CSS to form.css (was admin.css-only)

- Updated fragment routing to accept GET requests (needed for draft hydration)

app/src/Database.php

@@ -2016,7 +2016,7 @@ class Database
      * Return the raw FK fields not exposed through v_theses_full string columns.
      * Returns ['license_id', 'access_type_id', 'context_note'] or null if not found.
      *
-     * @return array{license_id:int|null,access_type_id:int|null,context_note:string}|null
+     * @return array{license_id:int|null,access_type_id:int|null,context_note:string,contact_visible:int|null}|null
      */
     public function getThesisRawFields(int $thesisId): ?array
     {