refactor(board-view): reorganize into modular folder structure

- Extract board-view into organized subfolders following new pattern:
  - components/: kanban-card, kanban-column
  - dialogs/: all dialog and modal components (8 files)
  - hooks/: all board-specific hooks (10 files)
  - shared/: reusable components between dialogs (model-selector, etc.)
- Rename all files to kebab-case convention
- Add barrel exports (index.ts) for clean imports
- Add docs/folder-pattern.md documenting the folder structure
- Reduce board-view.tsx from ~3600 lines to ~490 lines

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/app/src/components/views/board-view/dialogs/delete-completed-feature-dialog.tsx

@@ -0,0 +1,67 @@
+"use client";
+
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogFooter,
+  DialogHeader,
+  DialogTitle,
+} from "@/components/ui/dialog";
+import { Button } from "@/components/ui/button";
+import { Trash2 } from "lucide-react";
+import { Feature } from "@/store/app-store";
+
+interface DeleteCompletedFeatureDialogProps {
+  feature: Feature | null;
+  onClose: () => void;
+  onConfirm: () => void;
+}
+
+export function DeleteCompletedFeatureDialog({
+  feature,
+  onClose,
+  onConfirm,
+}: DeleteCompletedFeatureDialogProps) {
+  if (!feature) return null;
+
+  return (
+    <Dialog open={!!feature} onOpenChange={(open) => !open && onClose()}>
+      <DialogContent data-testid="delete-completed-confirmation-dialog">
+        <DialogHeader>
+          <DialogTitle className="flex items-center gap-2 text-destructive">
+            <Trash2 className="w-5 h-5" />
+            Delete Feature
+          </DialogTitle>
+          <DialogDescription>
+            Are you sure you want to permanently delete this feature?
+            <span className="block mt-2 font-medium text-foreground">
+              &quot;{feature.description?.slice(0, 100)}
+              {(feature.description?.length ?? 0) > 100 ? "..." : ""}&quot;
+            </span>
+            <span className="block mt-2 text-destructive font-medium">
+              This action cannot be undone.
+            </span>
+          </DialogDescription>
+        </DialogHeader>
+        <DialogFooter>
+          <Button
+            variant="ghost"
+            onClick={onClose}
+            data-testid="cancel-delete-completed-button"
+          >
+            Cancel
+          </Button>
+          <Button
+            variant="destructive"
+            onClick={onConfirm}
+            data-testid="confirm-delete-completed-button"
+          >
+            <Trash2 className="w-4 h-4 mr-2" />
+            Delete
+          </Button>
+        </DialogFooter>
+      </DialogContent>
+    </Dialog>
+  );
+}