refactor: consolidate blockchain explorer into single app and update backup ignore patterns

- Remove standalone explorer-web app (README, HTML, package files)
- Add /web endpoint to blockchain-explorer for web interface access
- Update .gitignore to exclude application backup archives (*.tar.gz, *.zip)
- Add backup documentation files to .gitignore (BACKUP_INDEX.md, README.md)
- Consolidate explorer functionality into main blockchain-explorer application

apps/marketplace/README.md

@@ -0,0 +1,41 @@
+# Marketplace Web
+
+Mock UI for exploring marketplace offers and submitting bids.
+
+## Development
+
+```bash
+npm install
+npm run dev
+```
+
+The dev server listens on `http://localhost:5173/` by default. Adjust via `--host`/`--port` flags in the `systemd` unit or `package.json` script.
+
+## Data Modes
+
+Marketplace web reuses the explorer pattern of mock vs. live data:
+
+- Set `VITE_MARKETPLACE_DATA_MODE=mock` (default) to consume JSON fixtures under `public/mock/`.
+- Set `VITE_MARKETPLACE_DATA_MODE=live` and point `VITE_MARKETPLACE_API` to the coordinator backend when integration-ready.
+
+### Feature Flags & Auth
+
+- `VITE_MARKETPLACE_ENABLE_BIDS` (default `true`) gates whether the bid form submits to the backend. Set to `false` to keep the UI read-only during phased rollouts.
+- `VITE_MARKETPLACE_REQUIRE_AUTH` (default `false`) enforces a bearer token session before live bid submissions. Tokens are stored in `localStorage` by `src/lib/auth.ts`; the API helpers automatically attach the `Authorization` header when a session is present.
+- Session JSON is expected to include `token` (string) and `expiresAt` (epoch ms). Expired or malformed entries are cleared automatically.
+
+Document any backend expectations (e.g., coordinator accepting bearer tokens) alongside the environment variables in deployment manifests.
+
+## Structure
+
+- `public/mock/offers.json` – sample marketplace offers.
+- `public/mock/stats.json` – summary dashboard statistics.
+- `src/lib/api.ts` – data-mode-aware fetch helpers.
+- `src/main.ts` – renders dashboard, offers table, and bid form.
+- `src/style.css` – layout and visual styling.
+
+## Submitting Bids
+
+When in mock mode, bid submissions simulate latency and always succeed.
+
+When in live mode, ensure the coordinator exposes `/v1/marketplace/offers`, `/v1/marketplace/stats`, and `/v1/marketplace/bids` endpoints compatible with the JSON shapes defined in `src/lib/api.ts`.