v1.8.4 — Backend proxy for POI Overpass queries (CORS fix)

Bugfix

POI markers still didn't appear after v1.8.3 because overpass-api.de blocks browser-based requests from private-LAN origins regardless of method (GET or POST) with HTTP 406 and no `Access-Control-Allow-Origin` header. The mirror fallback wasn't always helping either.

The fix: proxy through Home Assistant

Instead of the browser fetching Overpass directly (which triggers CORS), the request now goes through HA:

```
Browser ──ws──▶ Home Assistant ──https──▶ Overpass
```

The new websocket command `bosch_ebike/get_pois` runs the Overpass query server-side via `aiohttp` with:

• 35-second per-endpoint timeout
• Automatic fallback through three Overpass mirrors (overpass-api.de → kumi.systems → private.coffee)
• Proper User-Agent header
• Server-side logging of HTTP errors and Overpass rate-limit remarks

The browser only ever talks to HA (same origin), so CORS no longer applies.

Action after update

If your localStorage still has empty cached results from earlier failures, clear them once via the Web-Inspektor console:

```js
Object.keys(localStorage).filter(k=>k.startsWith("eb-poi-")).forEach(k=>localStorage.removeItem(k))
```

Installation

Update via HACS, restart Home Assistant (the new websocket command must be registered), then hard-refresh the browser (Cmd+Shift+R / Ctrl+Shift+R).