fix: add help email, preserve file names on validation error, license fix

The share link (partage) form does not expose a license field and does
not send access_type_id (defaults to 2/Interne). Server-side validation
was unconditionally requiring a license for non-admin submissions,
causing all share link submissions to fail.

Now the license check is gated on adminMode=false AND accessTypeId=1
(Libre), matching the client-side HTMX fragment behaviour in
licence-fragment.php. Also fixed a use-before-definition where
accessTypeId was referenced before being assigned.

Student form improvements:
- Add xamxam@erg.be mailto link at top of form
- On validation error, append "Si le problème persiste, envoyez un
  e-mail à xamxam@erg.be" to the flash message
- Preserve uploaded file names across validation redirects: store in
  session (share_primed_files_<slug>), display as warning on form
  re-render so the student knows which files to re-select

- License: only required for non-admin when access_type_id=1 (Libre),
  not for Interne (2) or Interdit (3). Fixes share link submissions
  failing with "Veuillez sélectionner une licence". Also fixed
  use-before-definition of accessTypeId.

app/storage/schema.sql

@@ -193,9 +193,6 @@ CREATE TABLE IF NOT EXISTS theses (
     -- External links
     baiu_link TEXT, -- Link to institutional repository
 
-    -- Home page card banner (optional, landscape image)
-    banner_path TEXT, -- path relative to STORAGE_ROOT (e.g. "banners/abc.jpg")
-
     -- Logistics checkboxes (backoffice only)
     exemplaire_baiu BOOLEAN DEFAULT 0,  -- Physical copy at BAIU
     exemplaire_erg BOOLEAN DEFAULT 0,  -- Physical copy at ERG
@@ -512,7 +509,6 @@ SELECT
     t.published_at,
     t.is_published,
     t.baiu_link,
-    t.banner_path,
     t.exemplaire_baiu,
     t.exemplaire_erg,
     t.cc2r,