Minor graphical improvements

- Uniform style of SVGs
- Add style directly inside SVGs to switch to dark mode - the previous solution didn't work in Chromium for some reason

templates/default/assets/light-bulb.svg

@@ -1 +1 @@
-<svg xmlns="http://www.w3.org/2000/svg" version="1.0" width="100" height="100" xml:space="preserve" xmlns:xlink="http://www.w3.org/1999/xlink"><g id="layer"><path d="m 50,9.999 c -14.729,0 -26.667,11.937 -26.667,26.667 0,3.609 0.729,7.066 2.041,10.208 l 7.959,19.214 v 17.246 c 0.0011,3.681625 2.985375,6.665896 6.667,6.667 h 20 c 3.68254,0.0011 6.668105,-2.98446 6.667,-6.667 V 66.095 L 74.629,46.874 C 75.976041,43.639385 76.668717,40.169891 76.667,36.666 76.667,21.936 64.733,9.999 50,9.999 Z M 61.600263,84.933676 H 38.39974 v -13.19983 l 23.200523,0.007 z M 70.069872,44.322 60.812246,66.668 H 39.187758 L 29.925949,44.306 C 28.915097,41.885903 28.396706,39.288723 28.400314,36.666 28.400314,25.637 38.972,15.066327 50,15.066327 c 11.028,0 21.599872,10.570673 21.599872,21.599673 0,2.643 -0.515,5.215 -1.53,7.656 z" id="path2" style="stroke-width:0;stroke-miterlimit:4;stroke-dasharray:none"/><path d="m 44.167,24.999 -7.5,20 h 17.047 l -5,13.334 h 7.119 l 7.5,-20.001 H 46.286 l 5,-13.333 z" id="path4" style="stroke-width:0;stroke-miterlimit:4;stroke-dasharray:none"/></g></svg>
+<svg xmlns="http://www.w3.org/2000/svg" xml:space="preserve" width="100" height="100" version="1.0"><style>@media (prefers-color-scheme:dark){*{stroke:#fff!important}}</style><path d="m30.208 71.296 39.584.008z" style="fill:none;fill-opacity:1;stroke:#000;stroke-width:5.51336;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1"/><path d="M50 2.5c-17.49 0-31.666 14.175-31.666 31.666 0 4.286.865 8.39 2.423 12.122l9.451 22.816v20.48a7.92 7.92 0 0 0 7.917 7.916h23.75a7.914 7.914 0 0 0 7.917-7.917v-20.47l9.454-22.825a31.49 31.49 0 0 0 2.42-12.122C81.666 16.675 67.495 2.5 50 2.5Z" style="fill:none;fill-opacity:1;stroke:#000;stroke-width:5;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1"/><path d="m50.19 58.72 10.654-22.314H39.535L50.19 18.061" style="fill:none;stroke:#000;stroke-width:5;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1;stroke-linecap:round"/></svg>