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/info.svg

@@ -0,0 +1,54 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
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+   height="40.905399mm"
+   viewBox="0 0 40.905399 40.905399"
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+   sodipodi:docname="info.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="1.4702524"
+     inkscape:cx="-31.287145"
+     inkscape:cy="44.550174"
+     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:#1e22ff;fill-opacity:1;stroke:#0003a0;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
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+</svg>