fix(uploader,setup): beta-test polish — crop overlay, sticker delete, emoji keyboard, copy

- crop: invert overlay shading; the destination-out trick on a
  semi-transparent fill was leaving the *inside* of the crop more
  transparent than the outside, so the keep-area read as darker
  than the discard-area. Replace with 4 explicit dim-strips.
- stickers: floating trash handle now glues to the selected
  sticker's top-right corner instead of an off-canvas X that
  testers missed.
- stickers: replace the curated grid with an emoji-keyboard
  picker — recently-used row, custom-sprite row (santa hat as
  inline SVG), then an input that pops the OS emoji keyboard.
  Recents persist in localStorage; legacy stickers fall back to
  the old STICKERS table.
- pwa-install modal: drop "browser chrome" — beta tester read it
  as the literal Chrome browser.
- /setup landing page: tighten "Set up your frame" copy.

frontend/src/views/SettingsView.vue

@@ -94,8 +94,8 @@
           </li>
         </ol>
         <p class="install-modal__footer">
-          The app will appear on your home screen and open without
-          browser chrome the next time you launch it.
+          The app will appear on your home screen. Open it from there
+          and it runs like a regular app — no address bar, no tabs.
         </p>
       </div>
     </div>