Fix two backend correctness issues

- Wrap setThesisJury() in a transaction: the method did a DELETE then multiple
  INSERTs with no atomicity guarantee. A partial failure (e.g. findOrCreateSupervisor
  throwing) would leave the jury table with orphaned rows. The fix uses
  pdo->inTransaction() to avoid nesting when called from within an outer transaction,
  and performs beginTransaction/commit/rollBack otherwise.

- Replace raw PDO query in admin/thanks.php with db->getThesisFiles(): the file
  listing after TFE submission was manually preparing a SELECT on thesis_files
  instead of calling the existing Database::getThesisFiles() method. Removes the
  getPDO() call entirely from that file.

TODO.md

@@ -408,7 +408,7 @@ Goal: rename the tables and column to the canonical M2M pattern (`tags`, `thesis
       into `$problematique` but the value is **never used** (no matching column, no INSERT reference).
       Deleted.
 
-- [ ] **`setThesisJury()` not wrapped in a transaction** — the method does a DELETE then multiple
+- [x] **`setThesisJury()` not wrapped in a transaction** — the method does a DELETE then multiple
       INSERTs with no transaction guard of its own. If called from outside a transaction (e.g. a
       future API endpoint) a partial failure leaves orphaned rows. Wrap the body in
       `BEGIN … COMMIT / ROLLBACK` (check `$this->pdo->inTransaction()` to avoid nesting).
@@ -551,7 +551,7 @@ Goal: rename the tables and column to the canonical M2M pattern (`tags`, `thesis
 
 ### H — Minor / low-hanging fruit
 
-- [ ] **`admin/thanks.php` duplicates `getThesisFiles()` with a raw PDO query** — lines 34–40
+- [x] **`admin/thanks.php` duplicates `getThesisFiles()` with a raw PDO query** — lines 34–40
       manually prepare `SELECT … FROM thesis_files WHERE thesis_id = ?` instead of calling
       `$db->getThesisFiles($thesisId)` which already exists. Replace with the DB method.
 

public/admin/thanks.php

@@ -25,7 +25,6 @@ if (isset($_GET['id'])) {
     if ($thesisId !== false && $thesisId > 0) {
         try {
             $db = new Database();
-            $pdo = $db->getPDO();
 
             // Get thesis data
             $thesis = $db->getThesis($thesisId);
@@ -33,15 +32,7 @@ if (isset($_GET['id'])) {
             if (!$thesis) {
                 $error = "TFE non trouvé.";
             } else {
-                // Get associated files
-                $stmt = $pdo->prepare("
-                    SELECT file_type, file_name, file_size, mime_type, uploaded_at
-                    FROM thesis_files
-                    WHERE thesis_id = ?
-                    ORDER BY file_type, uploaded_at
-                ");
-                $stmt->execute([$thesisId]);
-                $files = $stmt->fetchAll();
+                $files = $db->getThesisFiles($thesisId);
             }
         } catch (Exception $e) {
             error_log("Error loading thesis: " . $e->getMessage());

src/Database.php

@@ -812,6 +812,11 @@ class Database {
      * $juryMembers: array of ['name' => string, 'role' => string, 'is_external' => int]
      */
     public function setThesisJury(int $thesisId, array $juryMembers): void {
+        $alreadyInTransaction = $this->pdo->inTransaction();
+        if (!$alreadyInTransaction) {
+            $this->pdo->beginTransaction();
+        }
+        try {
             $this->pdo->prepare("DELETE FROM thesis_supervisors WHERE thesis_id = ?")->execute([$thesisId]);
             $stmt = $this->pdo->prepare("
                 INSERT INTO thesis_supervisors (thesis_id, supervisor_id, role, is_external, supervisor_order)
@@ -826,6 +831,15 @@ class Database {
                 $isExternal = isset($member['is_external']) ? (int)$member['is_external'] : 0;
                 $stmt->execute([$thesisId, $supervisorId, $role, $isExternal, $order + 1]);
             }
+            if (!$alreadyInTransaction) {
+                $this->pdo->commit();
+            }
+        } catch (\Throwable $e) {
+            if (!$alreadyInTransaction && $this->pdo->inTransaction()) {
+                $this->pdo->rollBack();
+            }
+            throw $e;
+        }
     }
 
     // ========================================================================