formulaire: correctifs identifiant/année, contact, fichiers optionnels

- Identifiant: mise à jour automatique quand l'année change en back-office (updateThesis + ThesisEditController)
- Contact: hint enrichi (1 seul contact, formatage Instagram/Mastodon)
- Fichiers: TFE rendu optionnel pour Site web/Performance/Installation (note d'intention reste obligatoire)

app/src/Controllers/ThesisEditController.php

@@ -217,6 +217,16 @@ class ThesisEditController
                 'cc2r'            => !empty($post['cc2r']),
                 'license_custom'  => trim($post['license_custom'] ?? ''),
             ];
+            // Regenerate identifier if year changed
+            $oldThesis = $this->db->getThesis($thesisId);
+            $oldYear = (int)($oldThesis['year'] ?? 0);
+            $newYear = $meta['year'];
+            if ($newYear !== $oldYear && $newYear >= 2000) {
+                $newIdentifier = $this->db->generateThesisIdentifier($newYear);
+                $meta['identifier'] = $newIdentifier;
+                error_log('[ThesisEdit] Year changed ' . $oldYear . ' → ' . $newYear . ', new identifier: ' . $newIdentifier);
+            }
+
             $this->db->updateThesis($thesisId, $meta);
             error_log('[ThesisEdit] Step 1 OK — thesis_id=' . $thesisId);