feat(styles): restructure UI styles and add main composition

New Features
- Added styles/main.css aggregating imports and global defaults
- Renamed battery.css → battery-widget.css for widget-specific styling

Enhancements
- Added smooth transitions and hover effects in panel.css
- Improved OSD styling with rounded corners, translucent background, and better spacing
- Updated button margins, paddings, and border‑radius for consistency

Bug Fixes
- Fixed missing border‑radius and spacing in panel buttons
- Corrected workspace button active/urgent styling

styles/main.css

@@ -0,0 +1,34 @@
+@import url("./colors.css");
+@import url("./panel.css");
+@import url("./dock.css");
+@import url("./switcher.css");
+@import url("./launcher.css");
+@import url("./osd.css");
+@import url("./controlcenter.css");
+@import url("./notification.css");
+@import url("./dropdown.css");
+@import url("./about.css");
+@import url("./notification-center.css");
+@import url("./player.css");
+@import url("./widgets.css");
+@import url("./tray.css");
+@import url("./battery-widget.css");
+@import url("./lock.css");
+@import url("./todo.css");
+
+* {
+    all: unset;
+    color: var(--foreground);
+    font-size: unset;
+    font-family: "SF Pro Rounded";
+}
+
+#corner {
+    background-color: var(--shadow);
+    border-radius: 0;
+}
+
+#corner-container {
+    min-width: 20px;
+    min-height: 20px;
+}