refactor(admin): make Admin remote-only, move device settings to Settings

A device administering itself via the Admin tool read as awkward, so the
local mode is gone and its options relocated to Settings.

- AdminScreen is remote-only: drop the CHOOSER phase, _local_mode, the
  LocalField/LocalKind model and activateLocalField/commitLocalField.
  Phases collapse to LOGIN/COMMAND/REPLY, entered only via startFor().
- Tools > Admin opens straight to the Nodes picker (ACT_ADMIN ->
  pickAdminTarget()). Backing out of a command screen returns to that
  picker; the picker's Cancel returns to Tools. gotoAdminScreen() removed.
- Settings > System gains Name (keyboard-edited node_name) and Reboot
  (action row, placed last so it isn't the default cursor). Radio + TX
  power were already in Settings; Send advert is the home ADVERT page.

Docs: tools_screen.md Admin section rewritten remote-only; settings_screen.md
System table gains Name + Reboot.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/solo_features/settings_screen/settings_screen.md

@@ -88,9 +88,11 @@ The **repeater** mode and its flood filters live on their own screen — see **T
 
 | Setting     | Options                                             | Notes                                                                                  |
 | ----------- | --------------------------------------------------- | -------------------------------------------------------------------------------------- |
+| Name        | keyboard entry (up to 31 chars)                     | This device's node name, shown to others and in every advert. **Enter** opens the keyboard pre-filled with the current name; applied and saved on submit |
 | Timezone    | −12 h … +14 h                                       | UTC offset in whole hours                                                              |
 | Low battery | off / 3.0 V / 3.1 V / 3.2 V / 3.3 V / 3.4 V / 3.5 V | Auto-shutdown threshold; also sets the 0 % anchor for the battery percentage indicator |
 | Units       | Metric / Imperial                                   | Global unit system for every distance/speed shown in Tools (Nearby Nodes, Trail, navigate-to-point). Metric: m / km, km/h, min/km. Imperial: ft / mi, mph, min/mi |
+| Reboot      | action (**Enter**)                                  | Restarts this device. Pending setting changes are saved first. Last row, so it isn't the default-selected one |
 
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