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/src/Controllers/TfeController.php

@@ -168,7 +168,7 @@ class TfeController
             'type'                   => 'article',
             'title'                  => $title,
             'description'            => $metaDescription,
-            'url'                    => self::BASE_URL . '/tfe.php?id=' . $thesisId,
+            'url'                    => self::BASE_URL . '/tfe?id=' . $thesisId,
             'image'                  => $ogImage,
             'image_alt'              => $imageAlt,
             'site_name'              => 'Posterg – ERG',
@@ -241,7 +241,7 @@ class TfeController
      */
     private function redirectHome(): never
     {
-        header('Location: index.php');
+        header('Location: /');
         exit;
     }
 }