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/index.ts

@@ -0,0 +1,8 @@
+export { AddFeatureDialog } from "./add-feature-dialog";
+export { AgentOutputModal } from "./agent-output-modal";
+export { CompletedFeaturesModal } from "./completed-features-modal";
+export { DeleteAllVerifiedDialog } from "./delete-all-verified-dialog";
+export { DeleteCompletedFeatureDialog } from "./delete-completed-feature-dialog";
+export { EditFeatureDialog } from "./edit-feature-dialog";
+export { FeatureSuggestionsDialog } from "./feature-suggestions-dialog";
+export { FollowUpDialog } from "./follow-up-dialog";