refactor: convert to bun workspaces monorepo

- Move web app into apps/web/
- Create packages/shared/ with shared types
- Create plugins/decky-vault/ scaffold
- Root package.json manages workspaces only

apps/web/lib/hooks/useDebounce.ts

@@ -0,0 +1,12 @@
+import { useState, useEffect } from "react"
+
+export function useDebounce<T>(value: T, delay: number): T {
+    const [debouncedValue, setDebouncedValue] = useState<T>(value)
+
+    useEffect(() => {
+        const timer = setTimeout(() => setDebouncedValue(value), delay)
+        return () => clearTimeout(timer)
+    }, [value, delay])
+
+    return debouncedValue
+}