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/public/home.php

@@ -1,7 +1,7 @@
 <?php if ($year): ?>
 <p class="filter-info" role="status">
     Année : <?= htmlspecialchars($year) ?>
-    <a href="?<?= http_build_query(array_diff_key($vars ?? [], ['page' => 1, 'year' => 1])) ?>" class="clear-filter"><span aria-hidden="true">✕</span> Réinitialiser</a>
+    <a href="/" class="clear-filter"><span aria-hidden="true">✕</span> Réinitialiser</a>
 </p>
 <?php elseif ($isDefaultView): ?>
 <p class="home-section-label" role="status">Publication récente</p>
@@ -24,7 +24,7 @@
                     ?>
                     <?php if ($thumb): ?>
                         <figure>
-                            <img src="/media.php?path=<?= urlencode($thumb) ?>"
+                            <img src="/media?path=<?= urlencode($thumb) ?>"
                                  alt="Couverture — <?= htmlspecialchars($item['title']) ?> par <?= htmlspecialchars($item['authors'] ?? '') ?>"
                                  loading="lazy">
                         </figure>