fix: skip marking, fixed panel ratio, dialog hints, 30s boot, ping+UDP fallback

- TftpSubStepFrame.set_step_skipped(): ◌ Skip in WARNING color
- _reload_config(): suppress callbacks to avoid duplicate log/status wipe
- _log_all_file_info(): removed clear_info(), updates in-place per-key
- Removed duplicate _log_file_info method
- main_frame grid: uniform col group for strict 7:3 ratio
- FileSelector browse title shows expected file type hint
- boot_wait_delay: default 10→30s
- Step 4 IP fallback: ping first, then UDP scan, extra boot_delay retry

src/config_manager.py

@@ -75,7 +75,7 @@ class Config:
     ping_count: int = 3
     uart_delay: int = 3
     inter_step_delay: int = 2
-    boot_wait_delay: int = 10
+    boot_wait_delay: int = 30
     step_timeouts: dict[str, int] = field(default_factory=lambda: {})
 
     # Internal: path to the config file on disk