Switching ui lib & refactoring (#80)

switch to shadcn ui
bump runtime versions (node, pnpm, etc)
refactor gui

src/lib/components/ui/avatar/avatar-fallback.svelte

@@ -0,0 +1,19 @@
+<script lang="ts">
+  import { Avatar as AvatarPrimitive } from 'bits-ui'
+  import { cn } from '$lib/utils'
+
+  type $$Props = AvatarPrimitive.FallbackProps
+
+  let className: $$Props['class'] = undefined
+  export { className as class }
+</script>
+
+<AvatarPrimitive.Fallback
+  class={cn(
+    'flex h-full w-full items-center justify-center rounded-full bg-muted',
+    className
+  )}
+  {...$$restProps}
+>
+  <slot />
+</AvatarPrimitive.Fallback>