Add stable firmware-update notifications and connected-device nudge

[RCGV1]

Parent: meshtastic/design#124

Implement the stable firmware-update nudge for the connected local device, following design#124 and the product workflow in Apple #2033.

Acceptance criteria

• Compare the connected device's reported version against the latest stable release using Meshtastic version ordering; do nothing for missing, malformed, equal, or newer current versions.
• Select the Web update flow or Meshtastic Flasher according to hardware capability, and name that destination in copy and accessibility metadata.
• Always show the connected-device nudge when eligible. Request no notification permission; create a browser notification only when permission has already been granted, deduped by (node identity, hardware target, stable version).
• Use the Material system_update_alt icon and neutral/accent update styling, never warning iconography or warning colors.
• Clear the nudge on disconnect, device change, or once the node is current.
• Add targeted tests for ordering, eligibility, dedupe, destination selection, notification permission behavior, and update—not-warning—presentation. Attach browser UI evidence.