Add Find Node buzzer admin action

[RCGV1]

What changed?

Adds a dedicated Find Node admin action for nodes with buzzer hardware:

• Adds AdminMessage.find_node_request handling to start/stop an audible find-node pattern.
• Returns find_node_response results for STARTED, STOPPED, NO_BUZZER, and BUZZER_DISABLED.
• Advertises DeviceMetadata.hasBuzzer so clients can gate the action by capability.
• Stops an active find-node pattern when local input is pressed on the node.
• Requires the normal admin/session-passkey path for remote admin use; direct local BLE/USB admin use follows existing local admin behavior.
• Preserves DeviceConfig reload semantics while ignoring stale deprecated/moved DeviceConfig fields (serial_enabled, is_managed) that older clients can echo back during sync.

Related PRs:

• Protobufs: Add Find Node buzzer admin protobufs protobufs#956
• Apple app: Add Find Node buzzer action Meshtastic-Apple#1973

Why did it change?

The phone app needs a clear phone-to-device contract to make a BLE-connected node buzz so the user can find it. A dedicated admin command is safer than overloading send_input_event or ringtone state, because firmware can return explicit capability/error results and can stop the pattern on real local user input.

T1000-E I2C/QMA and GPS fixes were intentionally removed from this PR because those are covered by separate PRs.

Verification

• trunk fmt ran via the commit hook on the touched files.
• ~/.platformio/penv/bin/python -m platformio test -e native-macos -f test_admin_radio passed after removing the I2C/GPS scope.
  • native-macos:test_admin_radio [PASSED].
  • 61 test cases, 61 succeeded in 85.677s.
• Branch diff was rechecked and contains no gps, i2c, qma, t1000, or motion files.

Attestations

• I have tested that my proposed changes behave as described.
• I have tested that my proposed changes do not cause any obvious regressions on the following devices:
  • Heltec (Lora32) V3
  • LilyGo T-Deck
  • LilyGo T-Beam
  • RAK WisBlock 4631
  • Seeed Studio T-1000E tracker card
  • Other (please specify below)

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