chore(web): delete dead tracked store.ts.backup (#2012)

`apps/web/lib/state/store.ts.backup` was a 1202-line snapshot of the
pre-slice-refactor monolithic Zustand store, accidentally committed in
b090a0157 (#1049). It never compiled and never ran — `tsconfig.json`
includes `**/*.ts`, which does not match a `.backup` suffix — so its only
effect was polluting grep/search results for anyone working on the real
store at `apps/web/lib/state/store.ts`.

No runtime code referenced it: `grep -rn "store.ts.backup" apps/` returns
nothing, and no build, lint, or tsconfig glob picks up `*.backup`.

Verified no logic was dropped. Of the 177 state keys and actions in the
backup, 172 exist in the live slice tree under `lib/state/slices/`. The
five that don't belong to two concepts that were deliberately renamed
after the snapshot was taken:

- `boardId` / `setBoards` / `setActiveBoard` — boards became workflows in
  658bd349b (#228); the live kanban slice uses `workflowId` /
  `setWorkflows` / `setActiveWorkflow`.
- `environmentsLoaded` / `setEnvironments` — environments became
  executors; the live settings slice has `ExecutorsState` /
  `setExecutors`.

Also add `*.backup`, `*.bak`, and `*.orig` to `.gitignore` so editor and
merge scratch copies cannot be committed again.

Co-authored-by: Kandev Agent <agent@kandev.dev>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitignore

@@ -28,6 +28,12 @@ __pycache__/
 *.swp
 *.swo
 *~
+
+# Editor/merge scratch copies. These never compile and only pollute grep
+# results for whoever works on the real file next.
+*.backup
+*.bak
+*.orig
 .DS_Store
 Thumbs.db