feat: licence page, admin pages editor, license types, gradient card placeholders, latest-year home view

- Feature 1: public /licence.php fetches 'licenses' page from DB, renders Markdown
- Feature 1: nav.php adds 'Licence' link with active state
- Feature 2: Database::getPage(), savePage(), getAllPages() methods
- Feature 2: bundled src/Parsedown.php (MIT, zero-dependency)
- Feature 2: apropos.php now renders 'about' page content from DB via Parsedown
- Feature 2: admin/pages.php (list) + admin/pages-edit.php (EasyMDE editor)
- Feature 2: admin/actions/page.php (auth+CSRF+validation+save)
- Feature 2: admin/head.php adds 'Pages statiques' nav link
- Feature 3: storage/schema.sql seeds 8 CC license types
- Feature 3: storage/migrations/003_seed_license_types.sql (applied to live DB)
- Feature 3: Database::getLicenseTypes() / getAllLicenseTypes()
- Feature 3: admin/add.php + formulaire.php: license_id field on add form
- Feature 3: admin/edit.php: license_id field on edit form with raw FK lookup
- Feature 3: tfe.php: shows 'Licence :' meta row when non-null
- Feature 6: main.css: .card__media--gradient styles
- Feature 6: index.php: deterministic HSL gradient placeholder cards
- Feature 6: Database::getLatestYearTheses() + getLatestPublishedYear()
- Feature 6: index.php default home = random latest-year theses with info label

public/admin/actions/formulaire.php

@@ -105,6 +105,9 @@ try {
     // Formats (optional, multiple selection)
     $formatIds = isset($_POST["formats"]) ? array_map('intval', $_POST["formats"]) : [];
 
+    // License
+    $licenseId = filter_var($_POST['license_id'] ?? '', FILTER_VALIDATE_INT) ?: null;
+
     // External link
     $lien = $_POST["lien"] ?? '';
     if (!empty($lien)) {
@@ -135,9 +138,9 @@ try {
             identifier, title, subtitle, year,
             orientation_id, ap_program_id, finality_id,
             synopsis, file_size_info,
-            baiu_link,
+            baiu_link, license_id,
             submitted_at
-        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP)
+        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP)
     ");
 
     $stmt->execute([
@@ -150,7 +153,8 @@ try {
         $finalityId,
         $synopsis,
         !empty($durationInfo) ? $durationInfo : null,
-        !empty($lien) ? $lien : null
+        !empty($lien) ? $lien : null,
+        $licenseId
     ]);
 
     $thesisId = $pdo->lastInsertId();