feat: electrs standalone install with bitcoin dependency + progress UI

- Add electrs to marketplace as standalone installable app
- Add dependency check: refuse install if no bitcoin node is running
- Use container DNS (bitcoin-knots:8332) on archy-net instead of host IP
- Auto-create bitcoin.conf with txindex + RPC on bitcoin-knots install
- Auto-build and start electrs-ui container post-install
- Show index size and estimated progress during initial sync
- Add /electrs-status and /health nginx proxy routes
- Remove Tailwind CDN from electrs-ui, use inline styles

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

neode-ui/src/views/Marketplace.vue

@@ -549,6 +549,17 @@ function getCuratedAppList() {
       manifestUrl: null,
       repoUrl: 'https://github.com/bitcoinknots/bitcoin'
     },
+    {
+      id: 'electrs',
+      title: 'Electrs',
+      version: 'latest',
+      description: 'Electrum protocol indexer for Bitcoin. Powers Mempool and other Electrum clients. Requires Bitcoin Knots or Bitcoin Core.',
+      icon: '/assets/img/app-icons/electrs.svg',
+      author: 'Roman Zeyde',
+      dockerImage: 'docker.io/mempool/electrs:latest',
+      manifestUrl: null,
+      repoUrl: 'https://github.com/romanz/electrs'
+    },
     {
       id: 'btcpay-server',
       title: 'BTCPay Server',