fix: make log viewer optional and document runtime dependencies

README.md

@@ -27,12 +27,19 @@ Supported actions:
 
 ## Requirements
 
+Required:
+
 - `bash`
 - `ssh`
 - `whiptail`
-- `nano`
 - `sed`
 - `tee`
+- core utilities such as `rm` and `touch`
+
+Optional log viewer:
+
+- `$EDITOR` if it points to an installed command
+- otherwise one of: `nano`, `vi`, `less`
 
 ## Install
 
@@ -101,5 +108,6 @@ Options:
 
 - SSH connections currently use `root@host`
 - The tool is interactive and intended for manual administration workflows
-- After execution, the log file is opened in `nano`
+- After execution, the log file is opened with `$EDITOR` when available, otherwise with `nano`, `vi`, or `less`
+- If no supported log viewer is available, the script keeps running and prints the log file path
 - The configuration file is sourced as shell code, so only use trusted config files