feat: energy flow, weather, comparison, PWA, alarm subs (v1.5.0)

7 new features inspired by iSolarCloud:

1. Animated Energy Flow Diagram — SVG/CSS animated power flow
   between PV, Load, Grid, HeatPump with real-time values
2. Weather Widget — temperature/condition on dashboard header
3. Curve Template Library — save/load Data Query presets
4. Enhanced Device Comparison — multi-device power overlay chart
5. Dispersion Rate Analysis — statistical variation across inverters
   with outlier detection (new Analysis tab)
6. PWA Support — manifest.json + service worker for mobile install
7. Alarm Subscription UI — configurable notification preferences

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/public/sw.js

@@ -0,0 +1,21 @@
+// Simple service worker for PWA installability
+const CACHE_NAME = 'zpark-ems-v1';
+
+self.addEventListener('install', (event) => {
+  self.skipWaiting();
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(clients.claim());
+});
+
+self.addEventListener('fetch', (event) => {
+  // Network-first strategy for API calls, cache-first for static assets
+  if (event.request.url.includes('/api/')) {
+    event.respondWith(fetch(event.request));
+  } else {
+    event.respondWith(
+      caches.match(event.request).then(response => response || fetch(event.request))
+    );
+  }
+});