feat: Phase 3 - filter bar, keyboard navigation, notifications, comments

- FilterBar component with text search, label chips, due date and priority dropdowns
- "/" keyboard shortcut and toolbar button to toggle filter bar
- Keyboard card navigation with J/K/H/L keys, Enter to open, Escape to clear
- Focus ring on keyboard-selected cards with auto-scroll
- Desktop notifications for due/overdue cards via tauri-plugin-notification
- CommentsSection component with add/delete and relative timestamps
- Filtered card count display in column headers

package.json

@@ -13,9 +13,11 @@
     "@dnd-kit/core": "^6.3.1",
     "@dnd-kit/sortable": "^10.0.0",
     "@dnd-kit/utilities": "^3.2.2",
+    "@tailwindcss/typography": "^0.5.19",
     "@tauri-apps/api": "^2",
     "@tauri-apps/plugin-dialog": "^2.6.0",
     "@tauri-apps/plugin-fs": "^2.4.5",
+    "@tauri-apps/plugin-notification": "^2.3.3",
     "@tauri-apps/plugin-opener": "^2",
     "@tauri-apps/plugin-shell": "^2.3.5",
     "class-variance-authority": "^0.7.1",
@@ -24,6 +26,8 @@
     "date-fns": "^4.1.0",
     "framer-motion": "^12.34.0",
     "lucide-react": "^0.564.0",
+    "overlayscrollbars": "^2.14.0",
+    "overlayscrollbars-react": "^0.5.6",
     "radix-ui": "^1.4.3",
     "react": "^19.1.0",
     "react-dom": "^19.1.0",