Add placeholder images, enhance alert styles, and implement theme toggle component with dark mode support

public/images/discord-icon.svg

@@ -0,0 +1,3 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 127.14 96.36">
+  <path fill="#5865f2" d="M107.7,8.07A105.15,105.15,0,0,0,81.47,0a72.06,72.06,0,0,0-3.36,6.83A97.68,97.68,0,0,0,49,6.83,72.37,72.37,0,0,0,45.64,0,105.89,105.89,0,0,0,19.39,8.09C2.79,32.65-1.71,56.6.54,80.21h0A105.73,105.73,0,0,0,32.71,96.36,77.7,77.7,0,0,0,39.6,85.25a68.42,68.42,0,0,1-10.85-5.18c.91-.66,1.8-1.34,2.66-2a75.57,75.57,0,0,0,64.32,0c.87.71,1.76,1.39,2.66,2a68.68,68.68,0,0,1-10.87,5.19,77,77,0,0,0,6.89,11.1A105.25,105.25,0,0,0,126.6,80.22h0C129.24,52.84,122.09,29.11,107.7,8.07ZM42.45,65.69C36.18,65.69,31,60,31,53s5-12.74,11.43-12.74S54,46,53.89,53,48.84,65.69,42.45,65.69Zm42.24,0C78.41,65.69,73.25,60,73.25,53s5-12.74,11.44-12.74S96.23,46,96.12,53,91.08,65.69,84.69,65.69Z"/>
+</svg>

public/images/google-icon.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 48 48">
+    <path fill="#EA4335" d="M24 9.5c3.54 0 6.71 1.22 9.21 3.6l6.85-6.85C35.9 2.38 30.47 0 24 0 14.62 0 6.51 5.38 2.56 13.22l7.98 6.19C12.43 13.72 17.74 9.5 24 9.5z"/>
+    <path fill="#4285F4" d="M46.98 24.55c0-1.57-.15-3.09-.38-4.55H24v9.02h12.94c-.58 2.96-2.26 5.48-4.78 7.18l7.73 6c4.51-4.18 7.09-10.36 7.09-17.65z"/>
+    <path fill="#FBBC05" d="M10.53 28.59c-.48-1.45-.76-2.99-.76-4.59s.27-3.14.76-4.59l-7.98-6.19C.92 16.46 0 20.12 0 24c0 3.88.92 7.54 2.56 10.78l7.97-6.19z"/>
+    <path fill="#34A853" d="M24 48c6.48 0 11.93-2.13 15.89-5.81l-7.73-6c-2.15 1.45-4.92 2.3-8.16 2.3-6.26 0-11.57-4.22-13.47-9.91l-7.98 6.19C6.51 42.62 14.62 48 24 48z"/>
+</svg>