Vendor platform-tools: everything this site runs is now in one repo

shared/platform-tools was a git submodule. On this branch it is a plain
directory of tracked files, frozen at ea3616abae30106df283e73a3e2f9e5bb0e6ae90
— the same commit fotografia.andmore.pt pins. Contents are byte-identical to
that tree, verified blob by blob.

The submodule caused every deployment failure this site has had:

  - .gitmodules named no `branch`, so the update fell back to
    refs/remotes/origin/HEAD — a ref a plain server-side clone never writes.
    "Atualizar submódulo" failed with "Unable to find refs/remotes/origin/HEAD
    revision in submodule path".
  - Its URL was http://, which the origin answers with 523.
  - This install is deployed by uploading files, and a submodule is invisible
    to that. The tree moved forward while shared/platform-tools stayed on the
    old pin, config/functions_secrets.php died on a missing compat_secrets.php,
    and the whole site — public pages included — went down.

Each of those was separately fixable. Together they mean a second repository
nobody can see from the deployment path, gating whether the first one boots. A
plain directory deploys like every other file and cannot fall out of step.

The cost is that platform-tools updates no longer arrive by bumping a pin; they
are a copy-over-and-commit. shared/platform-tools/VENDORED.md records the
upstream SHA, the procedure, and which four files differ from upstream in line
endings only (social/*.js, .css, functions_publications.php — CRLF upstream,
normalised to LF here; content otherwise identical).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

shared/platform-tools/api/backup_trigger.php

@@ -0,0 +1,55 @@
+<?php
+// Self-bootstrapping POST handler. Assumed location:
+//   <host>/shared/platform-tools/api/backup_trigger.php
+// dirname(__DIR__, 3) === <host>
+
+$repo_root = dirname(__DIR__, 3);
+require_once $repo_root . '/config/db.php';
+require_once $repo_root . '/config/functions.php';
+require_once $repo_root . '/config/functions_backup.php';
+require_once __DIR__ . '/../functions_csrf.php';
+require_once __DIR__ . '/../functions_settings.php';   // platform_admin_url()
+require_sysadmin();
+
+if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
+    header('Location: ' . platform_admin_url('backups.php'));
+    exit;
+}
+
+if (!platform_csrf_ok()) {
+    $_SESSION['backup_flash'] = [
+        'type'    => 'danger',
+        'message' => 'Pedido rejeitado (token CSRF ausente ou inválido). Recarrega a página e repete.',
+    ];
+    header('Location: ' . platform_admin_url('backups.php'));
+    exit;
+}
+
+$type = $_POST['type'] ?? '';
+
+if (!in_array($type, ['files', 'db'], true)) {
+    $_SESSION['backup_flash'] = [
+        'type'    => 'danger',
+        'message' => 'Tipo de backup inválido.',
+    ];
+    header('Location: ' . platform_admin_url('backups.php'));
+    exit;
+}
+
+$count_before = count(backup_list());
+$ok = backup_trigger($type);
+
+$_SESSION['backup_flash'] = $ok
+    ? [
+        'type'        => 'success',
+        'message'     => 'Backup iniciado. A lista atualiza automaticamente quando o ficheiro aparecer.',
+        // Lets the backups page poll until a new file shows up.
+        'await_count' => $count_before,
+      ]
+    : [
+        'type'    => 'danger',
+        'message' => 'Falha ao iniciar o backup. Verifique os logs do servidor.',
+      ];
+
+header('Location: ' . platform_admin_url('backups.php'));
+exit;