[ImgBot] Optimize images

*Total -- 4,659.87kb -> 4,503.61kb (3.35%)

/frontend/tests/assets/nextcloud-logo.png -- 163.47kb -> 87.99kb (46.17%)
/frontend/tests/assets/pingvin-share-logo.png -- 85.61kb -> 58.04kb (32.2%)
/backend/images/logo.svg -- 0.68kb -> 0.53kb (22.56%)
/frontend/tests/assets/clouds.jpg -- 577.56kb -> 528.14kb (8.56%)
/backend/images/background.jpg -- 3,832.55kb -> 3,828.92kb (0.09%)

Signed-off-by: ImgBotApp <ImgBotHelp@gmail.com>

backend/images/logo.svg

@@ -1,17 +1 @@
-<svg id="a"
+<svg xmlns="http://www.w3.org/2000/svg" id="a" viewBox="0 0 1015 1015"><path d="M506.6,0c209.52,0,379.98,170.45,379.98,379.96,0,82.33-25.9,160.68-74.91,226.54-48.04,64.59-113.78,111.51-190.13,135.71l-21.1,6.7-50.29-248.04,13.91-6.73c45.41-21.95,74.76-68.71,74.76-119.11,0-72.91-59.31-132.23-132.21-132.23s-132.23,59.32-132.23,132.23c0,50.4,29.36,97.16,74.77,119.11l13.65,6.61-81.01,499.24h-226.36V0h351.18Z"/><style>@media (prefers-color-scheme:dark){#a path{fill:#fff}}@media (prefers-color-scheme:light){#a path{fill:#000}}</style></svg>
-    xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1015 1015">
-    <path d="M506.6,0c209.52,0,379.98,170.45,379.98,379.96,0,82.33-25.9,160.68-74.91,226.54-48.04,64.59-113.78,111.51-190.13,135.71l-21.1,6.7-50.29-248.04,13.91-6.73c45.41-21.95,74.76-68.71,74.76-119.11,0-72.91-59.31-132.23-132.21-132.23s-132.23,59.32-132.23,132.23c0,50.4,29.36,97.16,74.77,119.11l13.65,6.61-81.01,499.24h-226.36V0h351.18Z" />
-    <style>
-     @media (prefers-color-scheme: dark) {
-            #a path {
-                fill: #ffffff;
-            }
-        }
-
-        @media (prefers-color-scheme: light) {
-            #a path {
-                fill: #000000;
-            }
-        }
-    </style>
-</svg>