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/add.php

@@ -18,6 +18,7 @@ try {
     $finalityTypes = $db->getAllFinalityTypes();
     $languages    = $db->getAllLanguages();
     $formatTypes  = $db->getAllFormatTypes();
+    $licenseTypes = $db->getAllLicenseTypes();
 } catch (Exception $e) {
     error_log("Failed to load form data: " . $e->getMessage());
     die("Erreur lors du chargement du formulaire.");
@@ -191,6 +192,20 @@ function wasSelected($key, $value) {
                       rows="7" required><?= old('synopsis') ?></textarea>
         </div>
 
+        <!-- Licence -->
+        <div class="admin-form-row">
+            <label class="admin-label" for="license_id">Licence :</label>
+            <select class="admin-select" id="license_id" name="license_id">
+                <option value="">— Inconnue —</option>
+                <?php foreach ($licenseTypes as $lt): ?>
+                    <option value="<?= htmlspecialchars($lt['id']) ?>"
+                        <?= wasSelected('license_id', $lt['id']) ? 'selected' : '' ?>>
+                        <?= htmlspecialchars($lt['name']) ?>
+                    </option>
+                <?php endforeach; ?>
+            </select>
+        </div>
+
         <!-- Durée/Taille -->
         <div class="admin-form-row">
             <label class="admin-label" for="duration_info">Durée / Taille :</label>