feat(ai): implement intelligent auto-tagging system

- Added multi-provider AI infrastructure (OpenAI/Ollama)
- Implemented real-time tag suggestions with debounced analysis
- Created AI diagnostics and database maintenance tools in Settings
- Added automated garbage collection for orphan labels
- Refined UX with deterministic color hashing and interactive ghost tags

keep-notes/hooks/use-debounce.ts

@@ -0,0 +1,17 @@
+import { useEffect, useState } 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;
+}