feat: jury composition + banner image upload

- migration 004: thesis_supervisors.role + is_external; view adds jury_president/jury_promoteurs/jury_lecteurs
- migration 005: theses.banner_path; view exposes t.banner_path and t.license_id
- Database: getThesisJury(), setThesisJury(), setBannerPath()
- admin/add.php: jury fieldset (président/promoteur/lecteurs + externe checkboxes, JS add/remove rows); banner file input
- admin/edit.php: jury fieldset pre-populated from DB; banner preview + remove checkbox + upload; multipart form
- admin/actions/formulaire.php: parse jury fields → setThesisJury(); banner upload to banners/
- tfe.php: three conditional jury rows (président·e, promoteur·ice, lecteur·ices)
- schema.sql: updated thesis_supervisors, theses, v_theses_full, v_theses_public definitions
- admin.css: fieldset, jury-row, jury-entry, btn-remove styles

public/assets/admin.css

@@ -584,3 +584,60 @@ html, body {
   flex-direction: column;
   gap: 1.5rem;
 }
+
+/* Jury fieldset */
+.admin-fieldset {
+  border: 1px solid #333;
+  border-radius: 4px;
+  padding: 1rem 1.25rem;
+  margin: .5rem 0 1rem;
+  background: rgba(255,255,255,.02);
+}
+
+.admin-fieldset-legend {
+  font-size: .82rem;
+  font-weight: 600;
+  letter-spacing: .04em;
+  text-transform: uppercase;
+  color: var(--admin-text-muted);
+  padding: 0 .5rem;
+}
+
+.admin-jury-row {
+  display: flex;
+  align-items: center;
+  gap: .75rem;
+  flex-wrap: wrap;
+}
+
+.admin-jury-list {
+  display: flex;
+  flex-direction: column;
+  gap: .5rem;
+}
+
+.admin-jury-entry {
+  display: flex;
+  align-items: center;
+  gap: .75rem;
+  flex-wrap: wrap;
+}
+
+.admin-jury-ext {
+  white-space: nowrap;
+}
+
+.admin-btn-remove {
+  background: none;
+  border: 1px solid #555;
+  color: var(--admin-text-muted);
+  border-radius: 3px;
+  padding: .2rem .45rem;
+  font-size: .8rem;
+  cursor: pointer;
+  line-height: 1;
+}
+.admin-btn-remove:hover {
+  border-color: #e55;
+  color: #e55;
+}