fix: light mode symbolic icon

dzgui/data/images/gtk/steam-tray-symbolic.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 640 640"><!--!Font Awesome Free 7.3.1 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free Copyright 2026 Fonticons, Inc.--><path d="M568 320C568 457 456.8 568 319.6 568C205.8 568 110 491.7 80.6 387.6L175.8 426.9C182.2 459 210.7 483.3 244.7 483.3C283.9 483.3 316.6 450.9 314.9 409.8L399.4 349.6C451.5 350.9 495.2 308.7 495.2 256.1C495.2 204.5 453.2 162.6 401.5 162.6C349.8 162.6 307.8 204.6 307.8 256.1L307.8 257.3L248.6 343C233.1 342.1 217.9 346.4 205.1 355.1L72 300.1C82.2 172.4 189.1 72 319.6 72C456.8 72 568 183 568 320zM227.7 448.3L197.2 435.7C202.8 447.3 212.5 456.5 224.4 461.5C251.3 472.7 282.2 459.9 293.4 433.1C298.8 420.1 298.9 405.8 293.5 392.8C288.1 379.8 278 369.6 265 364.2C252.1 358.8 238.3 359 226.1 363.6L257.6 376.6C277.4 384.8 286.8 407.5 278.5 427.3C270.2 447.2 247.5 456.5 227.7 448.3zM401.5 193.8C435.9 193.8 463.8 221.7 463.8 256.1C463.8 290.5 435.9 318.4 401.5 318.4C367.1 318.4 339.2 290.5 339.2 256.1C339.2 221.7 367.1 193.8 401.5 193.8zM401.6 302.8C427.4 302.8 448.4 281.8 448.4 256C448.4 230.2 427.4 209.2 401.6 209.2C375.8 209.2 354.8 230.2 354.8 256C354.8 281.8 375.8 302.8 401.6 302.8z"/></svg>