Enhance logging in CLI preflight checks

- Added logging statements to the `doctor`, `dry_run`, and `up` functions to indicate the start of preflight checks, improving user feedback during execution.
- Ensured consistent logging messages across different functions to enhance traceability and debugging capabilities.

src/gpu_rent/cli.py

@@ -130,6 +130,7 @@ def version() -> None:
 def doctor() -> None:
     """Preflight без create: Keystone, квота, flavor, диск, Civitai, манифесты."""
     try:
+        log("запускаю проверку…")
         checks = run_doctor()
     except GpuRentError as exc:
         _die(exc)
@@ -141,6 +142,7 @@ def doctor() -> None:
 def dry_run() -> None:
     """План без mutating-вызовов."""
     try:
+        log("запускаю проверку…")
         checks = run_doctor()
         _print_checks(checks)
         console.print("\n[bold]План[/bold]")
@@ -458,6 +460,7 @@ def up(
         from gpu_rent.prompts import MenuItem, prompt_menu
         from gpu_rent.varsfile import upsert_vars
 
+        log("запускаю проверку…")
         checks = run_doctor()
         code = _print_checks(checks, quiet=not verbose)
         if code != 0: