ha: add li3_battery HA integration, replacing van-li3-battery

The li3 BMS has a persistently marginal BLE link from any single fixed
vantage point on this Pi (onboard adapter, a USB dongle that turned out to
be BR/EDR-only, and the Athom ESPHome BT proxy even after moving it closer).
Move capture into HA proper so bluetooth.async_ble_device_from_address can
pick whichever known source currently has the device, instead of hardcoding
one. Protocol parsing ported verbatim from li3/van-li3-battery.

van-li3-battery is disabled on the Pi; its MQTT discovery entities were
cleared.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

ha/custom_components/li3_battery/strings.json

@@ -0,0 +1,17 @@
+{
+  "config": {
+    "step": {
+      "bluetooth_confirm": {
+        "description": "Add the Li3 battery `{name}`?"
+      },
+      "user": {
+        "data": {
+          "address": "Device"
+        }
+      }
+    },
+    "abort": {
+      "already_configured": "This battery is already configured"
+    }
+  }
+}