feat(ui): add Button, Modal, Spinner, Toast, and Tooltip components with styles

- Implemented Button component with various props for customization.
- Created Modal component with header, content, and footer subcomponents.
- Added Spinner component for loading indicators.
- Developed Toast component for displaying notifications.
- Introduced Tooltip component for contextual hints with keyboard shortcuts.
- Added corresponding CSS modules for styling each component.
- Updated index file to export new components.
- Configured TypeScript settings for the UI package.

packages/shared/src/components/channel/FileUploadDropZone.module.css

@@ -0,0 +1,105 @@
+/* Fills its parent completely — used as a full-window wrapper in
+   GuildsLayout so a drop anywhere in the Brycord viewport triggers
+   the overlay. The `display: contents`-style layout contract is
+   preserved by `height: 100%` + `width: 100%` so the inner tree
+   (which expects a block filling its parent) still lays out the
+   same as before. */
+.root {
+	position: relative;
+	display: flex;
+	flex-direction: column;
+	height: 100%;
+	width: 100%;
+	min-height: 0;
+}
+
+.overlay {
+	position: absolute;
+	inset: 0;
+	z-index: 1000;
+	display: flex;
+	align-items: center;
+	justify-content: center;
+	background-color: rgba(0, 0, 0, 0.6);
+	backdrop-filter: blur(3px);
+	pointer-events: none; /* let the drop event fall through to .root */
+	animation: fadeIn 120ms ease-out;
+}
+
+@keyframes fadeIn {
+	from {
+		opacity: 0;
+	}
+	to {
+		opacity: 1;
+	}
+}
+
+.card {
+	display: flex;
+	flex-direction: column;
+	align-items: center;
+	gap: 12px;
+	padding: 32px 40px;
+	background-color: var(--background-floating, #1a1b1e);
+	border: 2px dashed var(--brand-primary, #5865f2);
+	border-radius: 12px;
+	max-width: 420px;
+	text-align: center;
+	box-shadow: 0 20px 48px rgba(0, 0, 0, 0.6);
+	/* cap re-enable so the card itself doesn't block the drop event
+	   (though the overlay is pointer-events:none anyway). */
+	pointer-events: none;
+}
+
+.iconBadge {
+	display: flex;
+	align-items: center;
+	justify-content: center;
+	width: 72px;
+	height: 72px;
+	border-radius: 50%;
+	background-color: rgba(88, 101, 242, 0.15);
+	color: var(--brand-primary, #5865f2);
+	margin-bottom: 4px;
+}
+
+.title {
+	font-size: 18px;
+	font-weight: 700;
+	color: var(--text-primary, #fff);
+}
+
+.subtitle {
+	font-size: 13px;
+	line-height: 1.45;
+	color: var(--text-secondary, #a0a3a8);
+	max-width: 320px;
+}
+
+.hint {
+	display: inline-flex;
+	align-items: center;
+	gap: 8px;
+	margin-top: 4px;
+	padding: 6px 12px;
+	background-color: rgba(0, 0, 0, 0.4);
+	border-radius: 6px;
+	font-size: 12px;
+	font-weight: 500;
+	color: var(--text-primary, #fff);
+}
+
+.hintKey {
+	display: inline-flex;
+	align-items: center;
+	justify-content: center;
+	min-width: 18px;
+	height: 18px;
+	padding: 0 5px;
+	border-radius: 4px;
+	background-color: rgba(255, 255, 255, 0.15);
+	font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
+	font-size: 11px;
+	font-weight: 600;
+}