feat: single entry point routing — convert to front controller pattern

- Create app/public/index.php as front controller (bootstrap + Dispatcher)
- Rewrite app/router.php for PHP dev server → all non-asset requests to index.php
- Update Dispatcher to render full page layouts (head+header+view+footer)
- Move public view templates into templates/public/ (home, search, tfe, about, repertoire)
- Delete dead direct-access public/*.php files (apropos, search, tfe, licence, repertoire)
- Add clean URL routes to Dispatcher (/search, /tfe, /repertoire, /apropos, /licence, /media)
- Remove .php extensions from all internal links (header, views, templates, URLs)
- Update OG tags in controllers to use clean URLs
- Update nginx posterg.conf → front-controller try_files pattern, block direct .php access
- Update header.php and search-bar.php form actions to clean URLs
- Switch AboutController nav key from 'nav' to 'currentNav' for consistency

app/templates/partials/repertoire-index.php

@@ -46,7 +46,7 @@ function repToggleUrl(array $sets, string $dim, string $value): string {
     foreach ($sets['fi']    as $v) $params[] = 'fi[]=' . urlencode($v);
     foreach ($sets['kw']    as $v) $params[] = 'kw[]=' . urlencode($v);
     $qs = implode('&', $params);
-    return '/repertoire.php' . ($qs ? '?' . $qs : '');
+    return '/repertoire' . ($qs ? '?' . $qs : '');
 }
 
 $anyActive = !empty($activeSets['years']) || !empty($activeSets['ap'])
@@ -163,7 +163,7 @@ $hx = 'hx-target="#repertoire-index" hx-swap="outerHTML" hx-push-url="true" hx-i
         <?php else: ?>
             <?php foreach ($studentMap as $name => $id): ?>
             <li>
-                <a href="tfe.php?id=<?= (int)$id ?>" class="rep-entry rep-entry--link">
+                <a href="/tfe?id=<?= (int)$id ?>" class="rep-entry rep-entry--link">
                     <?= htmlspecialchars($name) ?>
                 </a>
             </li>