Refactor toast notifications and modal dialog implementation

- Updated SCSS for toast notifications to support multiple toast types (success, info, warning, error) and improved layout.
- Added new SVG icons for error, info, success, and warning notifications.
- Created separate HTML templates for toast notifications and modal dialogs.
- Enhanced the dev panel with buttons to test different toast notifications and modal dialogs.

backend/static/success.svg

@@ -0,0 +1,54 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
+   width="40.905399mm"
+   height="40.905399mm"
+   viewBox="0 0 40.905399 40.905399"
+   version="1.1"
+   id="svg1"
+   sodipodi:docname="success.svg"
+   inkscape:version="1.4 (86a8ad7, 2024-10-11)"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:svg="http://www.w3.org/2000/svg">
+  <sodipodi:namedview
+     id="namedview1"
+     pagecolor="#ffffff"
+     bordercolor="#666666"
+     borderopacity="1.0"
+     inkscape:showpageshadow="2"
+     inkscape:pageopacity="0.0"
+     inkscape:pagecheckerboard="true"
+     inkscape:deskcolor="#d1d1d1"
+     inkscape:document-units="mm"
+     inkscape:zoom="0.73512621"
+     inkscape:cx="-352.32046"
+     inkscape:cy="-74.13693"
+     inkscape:window-width="2560"
+     inkscape:window-height="1369"
+     inkscape:window-x="-8"
+     inkscape:window-y="828"
+     inkscape:window-maximized="1"
+     inkscape:current-layer="layer1" />
+  <defs
+     id="defs1" />
+  <g
+     inkscape:label="Layer 1"
+     inkscape:groupmode="layer"
+     id="layer1"
+     transform="translate(-80.178404,-120.49168)">
+    <circle
+       style="fill:#03b500;fill-opacity:1;stroke:#027500;stroke-width:7;stroke-linecap:butt;stroke-linejoin:bevel;stroke-dasharray:none;stroke-opacity:1;paint-order:stroke fill markers"
+       id="path2"
+       cx="100.6311"
+       cy="140.94438"
+       r="16.9527" />
+    <path
+       d="m 112.46328,132.63911 q -0.58288,-0.62262 -1.37771,-0.84782 -0.78159,-0.2252 -1.58967,-0.0397 -0.79483,0.17221 -1.41745,0.75509 l -11.962235,11.27338 -3.85494,-3.96092 q -0.596125,-0.60937 -1.390958,-0.82132 -0.781586,-0.21196 -1.576419,-0.0132 -0.794833,0.18546 -1.417452,0.78158 -0.609372,0.59613 -0.821328,1.39096 -0.211955,0.79484 -0.02649,1.58967 0.198708,0.79483 0.794833,1.4042 l 5.974495,6.14671 q 0.887563,0.91406 2.159296,0.94055 1.271733,0.0265 2.199038,-0.84782 l 14.174524,-13.36644 q 0.62262,-0.58288 0.84782,-1.36446 0.2252,-0.79484 0.0397,-1.58967 -0.17221,-0.80808 -0.75509,-1.4307 z"
+       id="text1"
+       style="font-size:27.1303px;font-family:'Arial Rounded MT Bold';-inkscape-font-specification:'Arial Rounded MT Bold, ';fill:#ffffff;stroke-width:13.4584;stroke-linejoin:round;paint-order:stroke fill markers"
+       aria-label="✔️" />
+  </g>
+</svg>