Refactor apropos/charte/licence pages: shared layout, TOC anchors, and UI polish

Unify the three public pages (à propos, charte, licence) onto a single
grid layout (.page-content) with sticky TOC sidebar, replacing the old
separate  /  /  markup.

- Merge about.php, charte.php, licence.php templates into shared
  .page-content / .content-section structure
- Add CommonMark HeadingPermalinkExtension for stable heading anchors
- Use SlugNormalizer for TOC links so they match rendered heading IDs
- Standardize link styling across content blocks: bold black, accent on
  hover (consistent with global link style)
- Fix code block wrapping: use pre-wrap instead of pre, constrain grid
  columns with min-width:0, auto scrollbar
- Fix apropos page grid placement: force content-section into column 2
  so contacts and credits stay in the content area, not the sidebar

Also includes accumulated WIP changes:
- Header gradient: hardcoded purple-to-green (replaces CSS variables)
- Search placeholder font
- Duration field: replace minutes/sec/heures with h:m:s time inputs
- TFE file optional for formats 1,4,6 with client-side JS toggle
- Licence form: em-dash to hyphen, details/summary classes
- Pill search: block Enter key form submission when no results
- Draft autosave: remove CSRF rotation (broke concurrent FilePond uploads)
- Language pill: clear hints for excluded main languages
- Search results: gradient placeholder cards for items without covers
- TFE display: format durée values as XhYm instead of decimal

app/templates/public/tfe.php

@@ -50,22 +50,25 @@
                 <?php
                 $_dVal = (float)$data["duration_value"];
                 $_dUnit = $data["duration_unit"];
-                $_unitLabels = [
-                    'pages'   => 'pages',
-                    'minutes' => 'minutes',
-                    'sec'     => 'secondes',
-                    'heures'  => 'heures',
-                    'mo'      => 'Mo',
-                ];
-                $_label = $_unitLabels[$_dUnit] ?? $_dUnit;
-                // if float, show 0.1 or .0 as needed
-                $_display = ($_dVal == (int)$_dVal) ? (int)$_dVal : $_dVal;
+                $_label = match($_dUnit) {
+                    'pages' => 'pages',
+                    'mo'    => 'Mo',
+                    'durée' => '',
+                    default => $_dUnit,
+                };
+                if ($_dUnit === 'durée') {
+                    $_hours = (int)floor($_dVal);
+                    $_mins = (int)round(($_dVal - $_hours) * 60);
+                    $_display = ($_mins > 0) ? "{$_hours}h{$_mins}" : "{$_hours}h";
+                } else {
+                    $_display = ($_dVal == (int)$_dVal) ? (int)$_dVal : $_dVal;
+                }
                 ?>
                 <p class="tfe-meta-item">
                     <span class="tfe-meta-label">Durée :</span>
-                    <?= $_display ?> <?= htmlspecialchars($_label) ?>
+                    <?= $_display ?><?= $_label ? ' ' . htmlspecialchars($_label) : '' ?>
                 </p>
-                <?php unset($_unitLabels, $_dVal, $_dUnit, $_label, $_display); endif; ?>
+                <?php unset($_dVal, $_dUnit, $_label, $_display, $_hours, $_mins); endif; ?>
 
                 <?php if (!empty($data["languages"])): ?>
                 <p class="tfe-meta-item">