feat: MAINT-001 - Fix Ruff violations across all Python source

tests/test_mining_cli.py

@@ -5,8 +5,6 @@ from __future__ import annotations
 import json
 import socket
 import sys
-import types
-from pathlib import Path
 from unittest.mock import MagicMock, patch
 
 # A fake node server has no real backend to prove capability with; say so
@@ -134,7 +132,6 @@ def test_print_models_table_runs_without_error(capsys, monkeypatch):
 def test_wizard_writes_config_on_happy_path(tmp_path, monkeypatch):
     "Wizard writes config on happy path\n\nTags: general"
     from meshnet_node import wizard as wiz
-    from meshnet_node.config import load_config, save_config
 
     # Fake GPU
     gpus = [{"index": 0, "name": "RTX 4090", "vram_gb": 24.0, "backend": "cuda"}]
@@ -265,7 +262,6 @@ def test_config_command_no_config_exits_1(tmp_path, monkeypatch):
 
 def test_config_command_prints_saved_config(tmp_path, monkeypatch, capsys):
     "Config command prints saved config\n\nTags: general"
-    from meshnet_node import config as cfg_mod
     from meshnet_node.config import save_config
     from meshnet_node.cli import main
 
@@ -309,7 +305,6 @@ def test_detect_num_layers_returns_none_on_error(monkeypatch):
 def test_startup_auto_detects_shard_range(monkeypatch, tmp_path):
     "When shard_start/end are None, startup reads layer count from catalog.\n\nTags: general"
     from meshnet_node import startup as su
-    from meshnet_node.model_catalog import detect_num_layers
 
     calls = []