Add KNX address validation and bcs metadata

custom_components/ha_knx_bridge/strings.json

@@ -3,6 +3,9 @@
     "abort": {
       "knx_not_configured": "Set up the Home Assistant KNX integration first."
     },
+    "error": {
+      "invalid_ga": "Invalid KNX group address. Use X/Y/Z (0-31/0-7/0-255) or X/Y (0-31/0-2047)."
+    },
     "step": {
       "user": {
         "title": "HA KNX Bridge",
@@ -13,7 +16,18 @@
       }
     }
   },
+  "options": {
+    "step": {
+      "init": {
+        "title": "HA KNX Bridge Options",
+        "description": "No options available yet."
+      }
+    }
+  },
   "config_subentries": {
+    "error": {
+      "invalid_ga": "Invalid KNX group address. Use X/Y/Z (0-31/0-7/0-255) or X/Y (0-31/0-2047)."
+    },
     "binary_sensor": {
       "step": {
         "user": {