admin/index.php: add server-side pagination (25/page)

- Add Database::getThesesListCount(array $filters) — runs the same WHERE
  clauses as getThesesList() but with COUNT(DISTINCT t.id); used to compute
  total pages without loading all rows.
- Extend Database::getThesesList() with $limit/$offset parameters; when
  $limit > 0 appends LIMIT/OFFSET and re-binds positional params individually
  to avoid the PDO mixed-style restriction.
- Fix getThesesList() SELECT: add LEFT JOIN access_types + at.name as
  access_type — the column was referenced in the template but never fetched.
- Wire admin/index.php: read ?page=, compute $totalPages/$offset, pass
  $perPage=25 + $offset to getThesesList(); include pagination.php partial
  below the table with filter-preserving $baseParams.
- Add result-count line (<p class="admin-list-meta">) showing "X–Y sur Z TFE"
  when multiple pages exist.
- Add .admin-body .pagination-wrap / .pagination-btn / .pagination-info styles
  to admin.css (scoped to .admin-body to avoid colliding with public pages).

public/assets/css/admin.css

@@ -343,6 +343,29 @@
   color: var(--text-primary);
 }
 
+.admin-maintenance-bar form {
+  display: inline;
+}
+
+/* Result-count line above the thesis table */
+.admin-list-meta {
+  color: var(--text-secondary);
+  font-size: 0.85rem;
+  margin-bottom: 0.5rem;
+}
+
+/* Empty-state message below the thesis table */
+.admin-empty {
+  color: var(--text-secondary);
+  padding: 1rem 0;
+}
+
+/* Identifier column in the thesis table */
+.admin-table-id {
+  color: var(--text-secondary);
+  font-size: 0.8rem;
+}
+
 /* ── Filters bar ────────────────────────────────────────────────────────── */
 .admin-filters {
   display: flex;
@@ -808,3 +831,52 @@
   color: var(--text-secondary);
   text-decoration: underline;
 }
+
+/* ── Pagination (admin list) ─────────────────────────────────────────────── */
+.admin-body .pagination-wrap {
+  display: flex;
+  justify-content: center;
+  align-items: center;
+  gap: 0.5rem;
+  padding: 1.5rem 0 0.5rem;
+}
+
+.admin-body .pagination-wrap ul {
+  display: flex;
+  gap: 0.25rem;
+  list-style: none;
+  margin: 0;
+  padding: 0;
+}
+
+.admin-body .pagination-btn {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  min-width: 2.75rem;
+  min-height: 2.75rem;
+  padding: 0 0.6rem;
+  border: 1px solid var(--border-secondary);
+  border-radius: 3px;
+  color: var(--text-primary);
+  font-size: 0.9rem;
+  text-decoration: none;
+  transition: border-color 0.15s, color 0.15s;
+}
+
+.admin-body .pagination-btn:hover:not(.disabled) {
+  border-color: var(--admin-purple);
+  color: var(--admin-purple);
+}
+
+.admin-body .pagination-btn.disabled {
+  opacity: 0.3;
+  cursor: not-allowed;
+  pointer-events: none;
+}
+
+.admin-body .pagination-info {
+  font-size: 0.9rem;
+  color: var(--text-secondary);
+  padding: 0 0.5rem;
+}