WATranslate v4.1 — Adaptive Mobile / WhatsApp-style Web UI

PURPOSE
Make the existing WATranslate web application behave naturally on iPhones
and other narrow mobile screens without changing the working backend.

MOBILE BEHAVIOR (<= 760px)
- Full-screen Chats list first
- Tap a contact -> full-screen conversation
- WhatsApp-style back button returns to Chats
- Larger touch targets and avatars
- Contact WhatsApp ID hidden in list to save space
- Compact mobile chat header
- Mobile-sized incoming/outgoing bubbles
- Composer optimized for iPhone Safari
- Safe-area support for notches / home indicator
- Uses 100dvh where supported so Safari toolbar changes do not break layout
- Archive/Delete/Restore menus remain available
- Reply-to-specific-message remains available
- Translation preview and manual Send remain available
- No Google / Meta / database behavior changed

DESKTOP
Desktop/two-column behavior remains unchanged.

FILES
Overwrite:
public/index.php
assets/app.js
public/assets/app.js

Add:
assets/mobile-v4.1.css
public/assets/mobile-v4.1.css

The package also contains the existing ui-v4.css files so extraction is safe.

DO NOT CHANGE
- root api.php wrapper
- public/api.php
- public/webhook.php
- config.php
- database
- Google credentials
- Meta credentials
- src/ files

INSTALL
1. Back up the current WATranslate folder.
2. Upload this ZIP into:
   public_html/whatsapp-server-translator/
3. Extract and overwrite.
4. On each iPhone reload the page. If necessary, close the browser tab and
   reopen it so Safari/Firefox drops the previous CSS/JS cache.

TEST
Phone portrait:
- chat list fills screen
- tap contact -> conversation fills screen
- back arrow -> chat list
- archive/delete menu works
- translate reply works
- translation preview works
- send works

Desktop:
- sidebar and conversation remain side-by-side as before.

No SQL migration is required.
