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/src/App.tsx

@@ -0,0 +1,64 @@
+import React from 'react'
+import { BrowserRouter as Router, Routes, Route, Link, Navigate } from 'react-router-dom'
+import { Button } from '@/components/ui/button'
+import BountyBoard from '@/pages/BountyBoard'
+import StakingDashboard from '@/pages/StakingDashboard'
+import DeveloperLeaderboard from '@/pages/DeveloperLeaderboard'
+import EcosystemDashboard from '@/pages/EcosystemDashboard'
+
+function App() {
+  return (
+    <Router>
+      <div className="min-h-screen bg-background">
+        {/* Navigation Header */}
+        <header className="border-b bg-card">
+          <div className="container mx-auto px-4 py-4">
+            <div className="flex items-center justify-between">
+              <div className="flex items-center space-x-4">
+                <h1 className="text-2xl font-bold text-primary">AITBC</h1>
+                <span className="text-muted-foreground">Developer Ecosystem</span>
+              </div>
+              <nav className="flex items-center space-x-2">
+                <Link to="/bounties">
+                  <Button variant="ghost">Bounty Board</Button>
+                </Link>
+                <Link to="/staking">
+                  <Button variant="ghost">Staking</Button>
+                </Link>
+                <Link to="/leaderboard">
+                  <Button variant="ghost">Leaderboard</Button>
+                </Link>
+                <Link to="/ecosystem">
+                  <Button variant="ghost">Ecosystem</Button>
+                </Link>
+              </nav>
+            </div>
+          </div>
+        </header>
+
+        {/* Main Content */}
+        <main className="container mx-auto">
+          <Routes>
+            <Route path="/" element={<Navigate to="/bounties" replace />} />
+            <Route path="/bounties" element={<BountyBoard />} />
+            <Route path="/staking" element={<StakingDashboard />} />
+            <Route path="/leaderboard" element={<DeveloperLeaderboard />} />
+            <Route path="/ecosystem" element={<EcosystemDashboard />} />
+          </Routes>
+        </main>
+
+        {/* Footer */}
+        <footer className="border-t bg-card mt-8">
+          <div className="container mx-auto px-4 py-6">
+            <div className="text-center text-sm text-muted-foreground">
+              <p>© 2024 AITBC Developer Ecosystem & DAO Grants System</p>
+              <p className="mt-1">Built with React, TypeScript, and Tailwind CSS</p>
+            </div>
+          </div>
+        </footer>
+      </div>
+    </Router>
+  )
+}
+
+export default App