feat(telemetry): map Sync State 0-4 to named states with threshold colors

Add value mappings (0 Disconnected, 1 Connected, 2 Syncing, 3 Tracking,
4 Full) and matching red->green thresholds to the Sync State panel, so the
line, tooltip, and legend render state names and colors instead of bare 0-4.
Keeps the minimal custom-key convention; only the Sync State panel changes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docker/telemetry/grafana/dashboards/ledger-data-sync.json

@@ -834,7 +834,69 @@
             "insertNulls": false,
             "showPoints": "auto",
             "pointSize": 3
-          }
+          },
+          "mappings": [
+            {
+              "type": "value",
+              "options": {
+                "0": {
+                  "text": "Disconnected",
+                  "color": "red",
+                  "index": 0
+                },
+                "1": {
+                  "text": "Connected",
+                  "color": "orange",
+                  "index": 1
+                },
+                "2": {
+                  "text": "Syncing",
+                  "color": "yellow",
+                  "index": 2
+                },
+                "3": {
+                  "text": "Tracking",
+                  "color": "blue",
+                  "index": 3
+                },
+                "4": {
+                  "text": "Full",
+                  "color": "green",
+                  "index": 4
+                }
+              }
+            }
+          ],
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              {
+                "color": "red",
+                "value": null
+              },
+              {
+                "color": "orange",
+                "value": 1
+              },
+              {
+                "color": "yellow",
+                "value": 2
+              },
+              {
+                "color": "blue",
+                "value": 3
+              },
+              {
+                "color": "green",
+                "value": 4
+              }
+            ]
+          },
+          "color": {
+            "mode": "thresholds"
+          },
+          "min": 0,
+          "max": 4
         },
         "overrides": []
       },