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>

docker-compose.yml

@@ -0,0 +1,17 @@
+services:
+  heatpump:
+    image: nginx:1.29-alpine
+    restart: unless-stopped
+    ports:
+      - "${HEATPUMP_PORT:-8080}:80"
+    volumes:
+      - ./html:/usr/share/nginx/html:ro
+      - ${HEATPUMP_CSV:-./history.csv}:/data/history.csv:ro
+      - ./nginx/default.conf:/etc/nginx/conf.d/default.conf:ro
+      - ./nginx/security-headers.conf:/etc/nginx/security-headers.conf:ro
+      - ./nginx/.htpasswd:/etc/nginx/.htpasswd:ro
+    healthcheck:
+      test: ["CMD", "wget", "-q", "-O", "/dev/null", "http://127.0.0.1/healthz"]
+      interval: 30s
+      timeout: 5s
+      retries: 3