feat: refactor Grafana alerting rules into a consolidated system module and update individual alert files

hosts/web-arm/modules/grafana/default.nix

@@ -28,11 +28,13 @@ let
 in
 {
   imports = [
-    ./alerting/disk_usage.nix
-    ./alerting/cpu_usage.nix
-    ./alerting/host_down.nix
-    ./alerting/inode_usage.nix
-    ./alerting/ram_usage.nix
+    # Individual alert files removed, now handled by alerting/system/default.nix
+    # ./alerting/disk_usage.nix
+    # ./alerting/cpu_usage.nix
+    # ./alerting/host_down.nix
+    # ./alerting/inode_usage.nix
+    # ./alerting/ram_usage.nix
+    ./alerting/system/default.nix # Added: Imports the consolidated system alerts module
     # ... other rule files can be added here ...
     ./datasources/victoriametrics.nix
   ];
@@ -99,7 +101,7 @@ in
     };
     provision = {
       alerting = {
-        rules.settings.groups = lib.mkMerge []; # Allows rule groups to be merged
+        rules.settings.groups = lib.mkMerge []; # Allows rule groups to be merged (including the one from system/default.nix)
         contactPoints = {
           settings = {
             apiVersion = 1; # As per Grafana provisioning API