feat!: new targets.json structure, add target status endpoint, move frontend to HTML file with table

BREAKING CHANGE: convert older targets.json file to new structure

targets.example.json

@@ -1,4 +1,10 @@
 {
-    "pc": "00:AA:BB:CC:DD:EE",
-    "server": "01:23:45:67:89:00"
+    "pc": {
+        "mac": "00:AA:BB:CC:DD:EE",
+        "ip": "192.168.0.1"
+    },
+    "server": {
+        "mac": "01:23:45:67:89:00",
+        "ip": "192.168.0.2"
+    }
 }