feat 🔌 shelly-mcp set_auth-Tool + Digest-Auth-Fallback (TP17 Geräte-PW)

- set_auth: setzt einheitliches Admin-PW (SHELLY_DEVICE_PW) via Shelly.SetAuth,
  realm=Geräte-ID, ha1=sha256("admin:realm:pw") pro Gerät; guarded (confirm/dry-run).
- _rpc: HTTP-Digest-Fallback (user admin) bei 401 → Geräte bleiben nach set_auth managebar.
- .env.example/README: SHELLY_DEVICE_PW dokumentiert (getrennt vom WLAN-PSK); Rollout mit PW-Schritt.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

mcp/shelly/.env.example

@@ -1,6 +1,7 @@
 # shelly-mcp config — copy to .env (gitignored) and fill in.
 SHELLY_IOT_SSID=dirtyvader-iot
 SHELLY_IOT_PSK=                # IOT SSID passphrase (from ap1 w2-iot). Required for set_sta.
+SHELLY_DEVICE_PW=              # uniform Shelly admin password (Shelly.SetAuth). Required for set_auth. Separate from the WLAN PSK.
 SHELLY_SWEEP=10.40.41.180-250  # discovery range (VLAN1 today)
 SHELLY_MCP_HOST=127.0.0.1
 SHELLY_MCP_PORT=3030