feat: Add search and filter UI components

- Created SearchBar component with debounced input
- Built FilterPanel component with controls for priority, completion, tags, and due date
- Added sort controls (field and direction)
- Implemented filter clear functionality
- Display search results with highlighted text
- Added GlobalSearch component for home page
- Integrated search and filter into list detail view
- Added CSS styles for search highlighting

Requirements: 6.1, 6.2, 6.3, 6.4, 8.1, 8.2, 8.3

app/globals.css

@@ -1,3 +1,12 @@
 @tailwind base;
 @tailwind components;
-@tailwind utilities;
+@tailwind utilities;
+
+/* Search highlight styles */
+mark {
+  background-color: #fef08a;
+  color: inherit;
+  padding: 0 2px;
+  border-radius: 2px;
+  font-weight: 500;
+}