feat(repeater): status-bar indicator, power-save lock, diag polish

- Status bar: blinking » indicator while relaying (new ICON_REPEATER), added to
  the 1 s blink cadence alongside the advert/trail markers.
- Power-save lock: a repeater must hear all traffic, so duty-cycle RX is forced
  off whenever client_repeat is on. Effective state = rx_powersave && !repeat,
  applied at boot, in applyPowerSave(), on the on-device toggle, and on the app's
  CMD_SET_RADIO_PARAMS. Settings shows "--" and blocks the toggle while repeating;
  the user's pref is preserved and restored when the repeater is switched off.
- Diagnostics: reset now uses the standard Hold-Enter one-item action menu (Back
  dismisses) instead of an Enter/Cancel popup; new "Errors" row decodes the
  Dispatcher ERR_EVENT_* flags (F/C/R, or OK).
- RepeaterScreen: drop the live stats block (they live on Diagnostics).
- Min-SNR load clamp tightened to the UI's -20..10 range.

Docs updated (settings_screen, tools_screen, FEATURES).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/solo_features/settings_screen/settings_screen.md

@@ -71,7 +71,7 @@ Lists all available home screen pages. For each entry:
 | SF        | 5–12       | LEFT/RIGHT. Spreading factor. |
 | BW        | 7.8–500 kHz | LEFT/RIGHT cycles the standard LoRa bandwidths. |
 | CR        | 5–8        | LEFT/RIGHT. Coding rate (4/5–4/8). |
-| Pwr save  | ON / OFF   | **Battery saver.** Hardware duty-cycle receive: the SX126x cycles RX↔sleep on its own and wakes on a preamble, cutting average RX current. Trades a little receive latency; leave OFF for lowest-latency reception. Requires an SX126x radio (otherwise stays on continuous RX). |
+| Pwr save  | ON / OFF   | **Battery saver.** Hardware duty-cycle receive: the SX126x cycles RX↔sleep on its own and wakes on a preamble, cutting average RX current. Trades a little receive latency; leave OFF for lowest-latency reception. Requires an SX126x radio (otherwise stays on continuous RX). **Forced off (shown as `--`) while the repeater is on** — a repeater must listen continuously; your setting is restored when the repeater is switched off. |
 | Auto pwr  | ON / OFF   | **Adaptive Power Control.** Lowers actual TX power on strong links to save energy, ramping back up — to the **TX Pwr** ceiling — on weak or lost links. Link quality comes from direct-message ACK SNR and, for channel messages (no ACK), from hearing a repeater rebroadcast your packet. The radio page / name bar shows the live power. Default OFF (fixed TX power). |
 
 The **repeater** mode and its flood filters live on their own screen — see **Tools › Repeater**.