fix: only active singleton node sends health reports

Both nodes of a site cluster were sending health reports. The standby
node (without the DeploymentManager singleton) reported 0 instances and
no connections, overwriting the active node's data in the aggregator.

Added IsActiveNode flag to ISiteHealthCollector, set by
DeploymentManagerActor on PreStart/PostStop. HealthReportSender skips
sending when the node is not active. Also ensured EnsureDclConnections
is called during startup batch creation so data connections survive
container restarts.

cli_issues.md

@@ -0,0 +1,17 @@
+# CLI Issues & Missing Features
+
+Log any bugs, unexpected behavior, or missing features in the ScadaLink CLI here.
+
+## Format
+
+```
+### [Short title]
+- **Command**: `scadalink <command>`
+- **Description**: What happened or what's missing
+- **Expected**: What should happen
+- **Error output** (if applicable):
+```
+
+---
+
+<!-- Add issues below this line -->