Add Open Graph and Twitter Card meta tags to all public pages

- templates/public/head.php: add centralised OG/Twitter tag rendering via $ogTags array;
  supports type, title, description, url, image, image_alt, site_name, article_author,
  article_published_time; twitter:card switches between summary_large_image / summary
  based on presence of og:image

- public/tfe.php: populate full article OG tags — og:type=article, canonical URL,
  og:image resolved from banner_path → first image file in thesis_files → omitted,
  og:image:alt, article:author, article:published_time (year-01-01); twitter:card
  summary_large_image when image present

- public/index.php, search.php, apropos.php, licence.php: add basic og:type=website
  tags (title, description, canonical url, site_name)

Sharing a thesis link on Slack, WhatsApp, iMessage, or any social platform will now
render a rich preview card with the thesis title, synopsis excerpt, and cover/banner image.

TODO.md

@@ -539,9 +539,11 @@ Goal: rename the tables and column to the canonical M2M pattern (`tags`, `thesis
       site blurb for `index.php`, synopsis excerpt for `tfe.php`, page content intro for
       `apropos.php`/`licence.php`. Necessary for search indexing and link preview cards.
 
-- [ ] **No Open Graph tags** - `tfe.php` is the ideal candidate for `og:title`, `og:description`
+- [x] **No Open Graph tags** - `tfe.php` now emits `og:type=article`, `og:title`, `og:description`,
-      (synopsis), `og:image` (banner or cover path through `/media.php`), `og:type=article`.
+      `og:url`, `og:image` (banner → first image file → none), `og:image:alt`, `og:site_name`,
-      Without them, sharing a thesis link on social media or messaging apps shows a blank preview.
+      `article:author`, `article:published_time`, plus `twitter:card`/`twitter:title`/`twitter:description`/
+      `twitter:image`. All other public pages (`index`, `search`, `apropos`, `licence`) emit basic
+      `og:type=website` tags. OG rendering is centralised in `templates/public/head.php` via `$ogTags` array.
 
 ### H - Minor / low-hanging fruit
 

public/apropos.php

@@ -26,6 +26,13 @@ $pd->setSafeMode(true);
 $aboutHtml = $pd->text($rawContent);
 $pageTitle = 'À Propos – Posterg';
 $metaDescription = 'À propos de Posterg, le répertoire des mémoires de fin d\'études de l\'erg – École de Recherches Graphiques de Bruxelles.';
+$ogTags = [
+    'type'        => 'website',
+    'title'       => $pageTitle,
+    'description' => $metaDescription,
+    'url'         => 'https://posterg.erg.be/apropos.php',
+    'site_name'   => 'Posterg – ERG',
+];
 $extraCss = ['assets/apropos.css'];
 ?>
 <?php include APP_ROOT . '/templates/public/head.php'; ?>

public/index.php

@@ -52,6 +52,13 @@ try {
 $currentNav = '';
 $pageTitle = 'Posterg – Mémoires de l\'ERG';
 $metaDescription = 'Posterg répertorie et valorise les mémoires de fin d\'études (TFE) de l\'erg – École de Recherches Graphiques de Bruxelles.';
+$ogTags = [
+    'type'        => 'website',
+    'title'       => $pageTitle,
+    'description' => $metaDescription,
+    'url'         => 'https://posterg.erg.be/',
+    'site_name'   => 'Posterg – ERG',
+];
 $extraCss = ['assets/main.css'];
 ?>
 <?php include APP_ROOT . '/templates/public/head.php'; ?>

public/licence.php

@@ -22,6 +22,13 @@ $html = $pd->text($content);
 
 $pageTitle = $licencePageTitle . ' – Posterg';
 $metaDescription = 'Informations sur les licences d\'utilisation des mémoires publiés sur Posterg, le répertoire des TFE de l\'erg.';
+$ogTags = [
+    'type'        => 'website',
+    'title'       => $pageTitle,
+    'description' => $metaDescription,
+    'url'         => 'https://posterg.erg.be/licence.php',
+    'site_name'   => 'Posterg – ERG',
+];
 $extraCss = ['assets/apropos.css'];
 ?>
 <?php include APP_ROOT . '/templates/public/head.php'; ?>

public/search.php

@@ -63,6 +63,13 @@ $currentNav = 'repertoire';
 $searchBarValue = $_GET['query'] ?? '';
 $pageTitle = 'Répertoire – Posterg';
 $metaDescription = 'Parcourez le répertoire des mémoires de fin d\'études (TFE) de l\'erg – École de Recherches Graphiques de Bruxelles. Recherche par année, orientation, atelier et mots-clés.';
+$ogTags = [
+    'type'        => 'website',
+    'title'       => $pageTitle,
+    'description' => $metaDescription,
+    'url'         => 'https://posterg.erg.be/search.php',
+    'site_name'   => 'Posterg – ERG',
+];
 $extraCss = ['assets/search.css'];
 ?>
 <?php include APP_ROOT . '/templates/public/head.php'; ?>

public/tfe.php

@@ -25,6 +25,37 @@ $metaDescription = mb_strlen($_synopsisRaw) > 160
     ? mb_substr($_synopsisRaw, 0, 157) . '…'
     : (empty($_synopsisRaw) ? 'Mémoire de fin d\'études – Posterg, répertoire des TFE de l\'erg.' : $_synopsisRaw);
 unset($_tfeAuthor, $_synopsisRaw);
+
+// --- Open Graph / Twitter Card tags ------------------------------------------
+$_ogBaseUrl = 'https://posterg.erg.be';
+// Resolve OG image: banner → first image file → none
+$_ogImage = '';
+if (!empty($data['banner_path'])) {
+    $_ogImage = $_ogBaseUrl . '/media.php?path=' . rawurlencode($data['banner_path']);
+} elseif (!empty($data['files'])) {
+    foreach ($data['files'] as $_f) {
+        $_ext = strtolower(pathinfo($_f['file_path'], PATHINFO_EXTENSION));
+        if (in_array($_ext, ['jpg', 'jpeg', 'png', 'gif', 'webp'])) {
+            $_ogImage = $_ogBaseUrl . '/media.php?path=' . rawurlencode($_f['file_path']);
+            break;
+        }
+    }
+    unset($_f, $_ext);
+}
+$ogTags = [
+    'type'                   => 'article',
+    'title'                  => $data['title'] . (!empty($data['authors']) ? ' – ' . $data['authors'] : ''),
+    'description'            => $metaDescription,
+    'url'                    => $_ogBaseUrl . '/tfe.php?id=' . $thesisId,
+    'image'                  => $_ogImage,
+    'image_alt'              => $data['title'] . (!empty($data['authors']) ? ' par ' . $data['authors'] : ''),
+    'site_name'              => 'Posterg – ERG',
+    'article_author'         => $data['authors'] ?? '',
+    'article_published_time' => !empty($data['year']) ? $data['year'] . '-01-01' : '',
+];
+unset($_ogBaseUrl, $_ogImage);
+// --- End Open Graph ----------------------------------------------------------
+
 $extraCss = ['assets/tfe.css'];
 ?>
 <?php include APP_ROOT . '/templates/public/head.php'; ?>

templates/public/head.php

@@ -7,6 +7,47 @@
     <?php if (!empty($metaDescription)): ?>
     <meta name="description" content="<?= htmlspecialchars($metaDescription) ?>">
     <?php endif; ?>
+    <?php
+    // Open Graph / Twitter Card tags — populated per-page via $ogTags array.
+    // Keys: type, title, description, url, image, image_alt, site_name, article_author, article_published_time
+    if (!empty($ogTags)):
+        $ogType        = $ogTags['type']                    ?? 'website';
+        $ogTitle       = $ogTags['title']                   ?? ($pageTitle ?? 'Posterg');
+        $ogDescription = $ogTags['description']             ?? ($metaDescription ?? '');
+        $ogUrl         = $ogTags['url']                     ?? '';
+        $ogImage       = $ogTags['image']                   ?? '';
+        $ogImageAlt    = $ogTags['image_alt']               ?? $ogTitle;
+        $ogSiteName    = $ogTags['site_name']               ?? 'Posterg – ERG';
+    ?>
+    <meta property="og:type"        content="<?= htmlspecialchars($ogType) ?>">
+    <meta property="og:site_name"   content="<?= htmlspecialchars($ogSiteName) ?>">
+    <meta property="og:title"       content="<?= htmlspecialchars($ogTitle) ?>">
+    <?php if (!empty($ogDescription)): ?>
+    <meta property="og:description" content="<?= htmlspecialchars($ogDescription) ?>">
+    <?php endif; ?>
+    <?php if (!empty($ogUrl)): ?>
+    <meta property="og:url"         content="<?= htmlspecialchars($ogUrl) ?>">
+    <?php endif; ?>
+    <?php if (!empty($ogImage)): ?>
+    <meta property="og:image"       content="<?= htmlspecialchars($ogImage) ?>">
+    <meta property="og:image:alt"   content="<?= htmlspecialchars($ogImageAlt) ?>">
+    <?php endif; ?>
+    <?php if (!empty($ogTags['article_author'])): ?>
+    <meta property="article:author" content="<?= htmlspecialchars($ogTags['article_author']) ?>">
+    <?php endif; ?>
+    <?php if (!empty($ogTags['article_published_time'])): ?>
+    <meta property="article:published_time" content="<?= htmlspecialchars($ogTags['article_published_time']) ?>">
+    <?php endif; ?>
+    <meta name="twitter:card"       content="<?= !empty($ogImage) ? 'summary_large_image' : 'summary' ?>">
+    <meta name="twitter:title"      content="<?= htmlspecialchars($ogTitle) ?>">
+    <?php if (!empty($ogDescription)): ?>
+    <meta name="twitter:description" content="<?= htmlspecialchars($ogDescription) ?>">
+    <?php endif; ?>
+    <?php if (!empty($ogImage)): ?>
+    <meta name="twitter:image"      content="<?= htmlspecialchars($ogImage) ?>">
+    <meta name="twitter:image:alt"  content="<?= htmlspecialchars($ogImageAlt) ?>">
+    <?php endif; ?>
+    <?php endif; ?>
     <link rel="icon" type="image/svg+xml" href="/assets/admin_favicon.svg">
     <link rel="stylesheet" href="assets/modern-normalize.min.css">
     <link rel="stylesheet" href="assets/common.css">