feat(freshrss): Move to its own namespace

feat(longhorn): Add ability to specify PVC namespace
refactor(freshrss): Simplify env variable declaration

kubenix-modules/custom/longhorn-volume.nix

@@ -5,6 +5,11 @@ let
       storage = lib.mkOption {
         type = lib.types.str;
       };
+
+      namespace = lib.mkOption {
+        type = lib.types.str;
+        default = "default";
+      };
     };
   };
 in
@@ -28,7 +33,7 @@ in
 
             claimRef = {
               inherit name;
-              namespace = "default";
+              namespace = longhornVolume.namespace;
             };
 
             csi = {