Add heatpump compressor cycle analysis web app

Static page that plots Home Assistant on/off history of the heatpump
compressor with pan/zoom, per-phase hover durations and statistics
(min/max/mean/median, total on-time, duty cycle) for the visible range.
English/German UI. Served by nginx in Docker with basic auth, CSP and
a healthcheck; Plotly is vendored locally.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

nginx/default.conf

@@ -0,0 +1,36 @@
+server {
+    listen 80;
+    server_name _;
+    root /usr/share/nginx/html;
+    index index.html;
+
+    server_tokens off;
+    charset utf-8;
+
+    gzip on;
+    gzip_comp_level 6;
+    gzip_types text/css text/csv application/javascript;
+
+    auth_basic "Heatpump";
+    auth_basic_user_file /etc/nginx/.htpasswd;
+
+    location / {
+        try_files $uri $uri/ =404;
+        include /etc/nginx/security-headers.conf;
+    }
+
+    # the CSV is mounted separately so it can be replaced without touching the app
+    location = /history.csv {
+        alias /data/history.csv;
+        default_type text/csv;
+        include /etc/nginx/security-headers.conf;
+    }
+
+    # unauthenticated liveness probe for the container healthcheck
+    location = /healthz {
+        auth_basic off;
+        access_log off;
+        default_type text/plain;
+        return 200 "ok\n";
+    }
+}