branding: add EverShelf logo to kiosk splash + web header/preloader

- assets/img/logo/logo.png: trimmed full logo (icon + text, transparent bg)
- assets/img/logo/logo_icon.png: icon-only crop (no text, for header)
- drawable-*/ic_logo.png: multi-density PNGs for Android splash (mdpi→xxxhdpi)
- activity_kiosk.xml: replace ic_launcher_foreground with ic_logo at 260dp,
  remove redundant 'EverShelf' text row (already in logo image)
- index.html: add logo_icon.png in header title, logo.png in preloader
- style.css: add .app-preloader-logo and .header-logo-icon rules

evershelf-kiosk/app/src/main/res/layout/activity_kiosk.xml

@@ -14,20 +14,13 @@
         android:visibility="visible">
 
         <ImageView
-            android:layout_width="120dp"
-            android:layout_height="120dp"
-            android:src="@drawable/ic_launcher_foreground"
-            android:layout_marginBottom="24dp"
-            android:contentDescription="EverShelf" />
-
-        <TextView
-            android:layout_width="wrap_content"
+            android:layout_width="260dp"
             android:layout_height="wrap_content"
-            android:text="EverShelf"
-            android:textColor="#f1f5f9"
-            android:textSize="32sp"
-            android:textStyle="bold"
-            android:layout_marginBottom="8dp" />
+            android:src="@drawable/ic_logo"
+            android:adjustViewBounds="true"
+            android:scaleType="fitCenter"
+            android:layout_marginBottom="16dp"
+            android:contentDescription="EverShelf" />
 
         <TextView
             android:layout_width="wrap_content"