fix: container stack installers, DNS resolution, uninstall cleanup

- Replace aardvark-dns container names with host.containers.internal
  for all cross-app connections (LND→Bitcoin, ElectrumX→Bitcoin,
  Mempool→ElectrumX, Fedimint→Bitcoin, NBXplorer→Bitcoin P2P+RPC)
- Add BTCPay multi-container stack installer (postgres + nbxplorer +
  btcpay-server) with proper secrets, data dir ownership, NOAUTH
- Add Mempool multi-container stack installer (mariadb + mempool-api +
  mempool-frontend) with host.containers.internal for RPC
- Immediately remove apps from state on uninstall (no 3-min ghost delay)
- Include archy-bitcoin-ui in bitcoin uninstall container list
- Fix LND UI port 8081 (was 8080, conflicting with LND gRPC)
- Fix ElectrumX UI: proxy /electrs-status to backend, cache-busting
  headers, graceful fallback when backend returns HTML
- Add Tor hidden services for ElectrumX and LND in torrc template
- Remove unused detect_bitcoin_container_name() (replaced by
  host.containers.internal)

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

docker/electrs-ui/index.html

@@ -355,11 +355,15 @@
 
         async function updateStatus() {
             try {
-                var resp = await fetch('/electrs-status');
+                var resp = await fetch('/electrs-status', { cache: 'no-store' });
                 if (!resp.ok) {
                     throw new Error('Backend unavailable (HTTP ' + resp.status + ')');
                 }
-                var data = await resp.json();
+                var text = await resp.text();
+                if (text.trim().charAt(0) !== '{') {
+                    throw new Error('Waiting for Archipelago backend...');
+                }
+                var data = JSON.parse(text);
 
                 // Extract Tor onion from status response
                 if (data.tor_onion && !torOnion) {

docker/electrs-ui/nginx.conf

@@ -5,9 +5,17 @@ server {
     root /usr/share/nginx/html;
     index index.html;
 
-    # electrs-status is fetched via absolute /electrs-status path,
-    # handled by the host nginx → backend at :5678 directly
+    location /electrs-status {
+        proxy_pass http://127.0.0.1:5678/electrs-status;
+        proxy_http_version 1.1;
+        proxy_set_header Host $host;
+        proxy_connect_timeout 10s;
+        proxy_read_timeout 10s;
+        add_header Cache-Control "no-store, no-cache, must-revalidate";
+    }
+
     location / {
+        add_header Cache-Control "no-cache";
         try_files $uri $uri/ /index.html;
     }
 }

docker/lnd-ui/nginx.conf

@@ -1,5 +1,5 @@
 server {
-    listen 8080;
+    listen 8081;
     server_name _;
 
     root /usr/share/nginx/html;