Rebrand to QRForge (local only - do not push before domain confirmed)

Applies the approved QRForge brand kit throughout the app:
- New logo/icon SVGs, favicon set (ico/svg/png), apple-touch-icon, all
  copied from the approved brand kit into src/dist/img/brand/. Old
  Symbol_WhiteBlue.png/DynamicQRCode_Original.png removed (unused after
  the swap).
- Sidebar brand image/text, login and change-password page logos, all
  <title> tags, manifest.json name/theme-color, and the PWA icons
  (dist/img/icon-192.png/icon-512.png, same filenames so no other
  reference needed to change) updated to QRForge branding and the
  #2563EB brand blue.
- New about.php page (+ sidebar link): credits the original upstream
  fork (Giandonato Inverso) and chillerlan/php-qrcode, links to the free
  qr.ensembia.com try-out, the commercial www.qrforge.eu product page,
  and this GitHub repo for self-hosters.
- Footer now reads "QRForge" + "About / credits" + "Version 3.0"
  (replaces the inherited "PHP Qrcode Generator by Giandonato Inverso" /
  "Version 2.3.0" line - full credit moved to the About page instead).
- README.md rewritten: current feature set (all 16 static qr types,
  presets, scanner, PWA, location search, roles), qr.ensembia.com as the
  free try-out, www.qrforge.eu as the commercial product page, corrected
  Docker Compose setup steps (.env is required now, the old README still
  described the single-file demo setup from the original upstream fork).

IMPORTANT: not pushed to origin/gitea. Per user instruction, no push
until qrforge.eu domain registration is confirmed.

src/includes/sidebar.php

@@ -2,9 +2,9 @@
   <aside class="main-sidebar sidebar-dark-primary elevation-4">
     <!-- Brand Logo -->
     <a href="./index.php" class="brand-link">
-      <img src="dist/img/Symbol_WhiteBlue.png" alt="Logo" class="brand-image"
+      <img src="dist/img/brand/icon-inverse.svg" alt="QRForge" class="brand-image"
            style="opacity: .8">
-      <span class="brand-text font-weight-light">Qrcode Generator</span>
+      <span class="brand-text font-weight-light">QRForge</span>
     </a>
 
     <!-- Sidebar -->
@@ -109,6 +109,12 @@
             </a>
           </li>
           <?php endif; ?>
+          <li class="nav-item">
+            <a href="./about.php" <?php echo (CURRENT_PAGE == 'about.php') ? ' class="nav-link active"' : ' class="nav-link"'; ?>>
+                <i class="fas fa-info-circle nav-icon"></i>
+              <p>About</p>
+            </a>
+          </li>
         </ul>
       </nav>
       <!-- /.sidebar-menu -->