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

src/components/board/KanbanColumn.tsx

@@ -25,11 +25,13 @@ const WIDTH_MAP = {
 
 interface KanbanColumnProps {
   column: Column;
+  filteredCardIds?: string[];
+  focusedCardId?: string | null;
   onCardClick?: (cardId: string) => void;
   isNew?: boolean;
 }
 
-export function KanbanColumn({ column, onCardClick, isNew }: KanbanColumnProps) {
+export function KanbanColumn({ column, filteredCardIds, focusedCardId, onCardClick, isNew }: KanbanColumnProps) {
   const [showAddCard, setShowAddCard] = useState(false);
   const board = useBoardStore((s) => s.board);
   const toggleColumnCollapse = useBoardStore((s) => s.toggleColumnCollapse);
@@ -62,6 +64,8 @@ export function KanbanColumn({ column, onCardClick, isNew }: KanbanColumnProps)
       ? `3px solid ${board.color}30`
       : undefined;
 
+  const displayCardIds = filteredCardIds ?? column.cardIds;
+  const isFiltering = filteredCardIds != null;
   const cardCount = column.cardIds.length;
 
   const wipTint = column.wipLimit != null
@@ -117,7 +121,7 @@ export function KanbanColumn({ column, onCardClick, isNew }: KanbanColumnProps)
     >
       {/* The column header is the drag handle for column reordering */}
       <div {...listeners}>
-        <ColumnHeader column={column} cardCount={column.cardIds.length} />
+        <ColumnHeader column={column} cardCount={cardCount} filteredCount={isFiltering ? displayCardIds.length : undefined} />
       </div>
 
       {/* Card list - wrapped in SortableContext for within-column sorting */}
@@ -138,7 +142,7 @@ export function KanbanColumn({ column, onCardClick, isNew }: KanbanColumnProps)
             initial="hidden"
             animate="visible"
           >
-            {column.cardIds.map((cardId) => {
+            {displayCardIds.map((cardId) => {
               const card = board?.cards[cardId];
               if (!card) return null;
               return (
@@ -148,13 +152,14 @@ export function KanbanColumn({ column, onCardClick, isNew }: KanbanColumnProps)
                     boardLabels={board?.labels ?? []}
                     columnId={column.id}
                     onCardClick={onCardClick}
+                    isFocused={focusedCardId === cardId}
                   />
                 </li>
               );
             })}
-            {column.cardIds.length === 0 && (
+            {displayCardIds.length === 0 && (
               <li className="flex min-h-[60px] items-center justify-center rounded-md border border-dashed border-pylon-text-secondary/20 text-xs text-pylon-text-secondary/50">
-                Drop or add a card
+                {isFiltering ? "No matching cards" : "Drop or add a card"}
               </li>
             )}
           </motion.ul>