feat: add ~/.local/bin support for user scripts

Configure PATH and backup strategy for non-declarative user scripts.

- Add ~/.local/bin to sessionPath in global home-manager config
- Include ~/.local/bin in onsite borgbackup (hourly to viridian)
- Include ~/.local/bin in offsite borgbackup (daily to borgbase)

home-manager/sajenim/global/default.nix

@@ -39,6 +39,9 @@
     sessionVariables = {
       EDITOR = "nvim"; # Default text editor for CLI operations
     };
+    sessionPath = [
+      "$HOME/.local/bin" # User scripts and executables
+    ];
   };
 
   # Automatically restart systemd user services on configuration changes