Fase 3 feedback round: style preview, icon upload, font choice, optional bitcoin amount, WPA3

- Default the Owner select to the creator's own account instead of "All", so
  superadmin-created codes no longer silently become visible to every admin
  (the underlying NULL-fallback sharing behavior for an explicit "All" choice
  is unchanged).
- Add a live color/precision/size preview swatch next to the preset picker.
- Let the frame text use a chosen DejaVu font + font size instead of a fixed
  GD bitmap font.
- Add an optional self-uploaded icon rendered above the qr code (not embedded
  in it, so scanability is unaffected).
- Make the Bitcoin qr amount optional; a standing wallet address is useful
  without forcing a one-off amount per code.
- Add a WPA3 option to the WiFi qr encryption select.
- Fix a real bug surfaced while testing the preview/style JS: qrcode_options.php
  was included once per static qr type (16 times on one page) and each
  inclusion re-executed <script src="qrcode-style-tools.js">, so every button
  click fired once per type - e.g. saving one preset wrote 16 duplicate rows,
  and every tab except the first ("Text") had dead random-style/preset
  buttons since only the first DOM match ever got a listener. Moved the
  script include to load once per page and rewrote the JS to scope every
  lookup to the triggering element's own tab-pane/form instead of relying on
  getElementById's first-match behavior.

src/helpers/helpers.php

@@ -117,6 +117,45 @@ function paginationLinks($current_page, $total_pages, $base_url) {
 	return $html;
 }
 
+/**
+ * Handles the optional "icon above the qr code" upload. Validates the actual image
+ * type (not just the extension/mime the browser claims) and stores the file outside
+ * the document root, next to the generated qr codes.
+ */
+function qr_handle_icon_upload($fileKey = 'icon') {
+    if (!isset($_FILES[$fileKey]) || $_FILES[$fileKey]['error'] === UPLOAD_ERR_NO_FILE) {
+        return ['ok' => true, 'path' => null];
+    }
+
+    if ($_FILES[$fileKey]['error'] !== UPLOAD_ERR_OK) {
+        return ['ok' => false, 'error' => 'Icon upload failed.'];
+    }
+
+    if ($_FILES[$fileKey]['size'] > 1024 * 1024) {
+        return ['ok' => false, 'error' => 'Icon must be smaller than 1MB.'];
+    }
+
+    $info = @getimagesize($_FILES[$fileKey]['tmp_name']);
+    $allowed = [IMAGETYPE_PNG => 'png', IMAGETYPE_JPEG => 'jpg', IMAGETYPE_GIF => 'gif'];
+
+    if ($info === false || !isset($allowed[$info[2]])) {
+        return ['ok' => false, 'error' => 'Icon must be a PNG, JPEG or GIF image.'];
+    }
+
+    $dir = SAVED_QRCODE_DIRECTORY . 'icons/';
+    if (!is_dir($dir)) {
+        mkdir($dir, 0750, true);
+    }
+
+    $destination = $dir . bin2hex(random_bytes(16)) . '.' . $allowed[$info[2]];
+
+    if (!move_uploaded_file($_FILES[$fileKey]['tmp_name'], $destination)) {
+        return ['ok' => false, 'error' => 'Could not store the uploaded icon.'];
+    }
+
+    return ['ok' => true, 'path' => $destination];
+}
+
 function base_url() {
     require_once(__DIR__ . '/../config/environment.php');
     if (defined('BASE_URL') && BASE_URL !== null) {