feat(task): rename TASK_CONFIG_DIR to TASK_DOTENV_DIR and update related functions

- Replace all instances of `TASK_CONFIG_DIR` with `TASK_DOTENV_DIR` across environment-related scripts
- Update `init-config-dir` function name to `init-dotenv-dir` for consistency
- Adjust documentation and help table entries to reflect the renamed variable and function
- Maintain existing functionality and code style throughout affected scripts

task.template

@@ -9,7 +9,7 @@ help-table() {
     printf "$column" "Command" "Option" "Description"
     echo "|$(printf '%*s' $((cmd_width + 2)) '' | tr ' ' '-')|$(printf '%*s' $((opt_width + 2)) '' | tr ' ' '-')|$(printf '%*s' $((desc_width + 2)) '' | tr ' ' '-')|"
     # Task
-    printf "$column" 'init-config-dir' '' 'Setup task file config dir.'
+    printf "$column" 'init-dotenv-dir' '' 'Setup task dotenv dir.
     printf "$column" 'template-dotenv' '' 'Generate .env from .env.template.'
     printf "$column" 'open-with-os' '' 'Open file or url with default application.'
     printf "$column" 'open-url-with-delay' '[url][delay]' 'Open url after n seconds.'