linux: show battery for all connected AirPods in the tray

[bissamiftikhar]

Fixes #670

Problem

The tray tracked battery as a single global string. With two AirPods connected at the same time, whichever device updated last simply overwrote the other one in the tooltip, and on top of that bleDeviceFound() let a BLE proximity broadcast that matches the stored IRK override the state of the device the app is actually connected to — the broadcast is anonymized, so it may well belong to a different paired device sitting in its case nearby. That's the "AirPods Pro 2 superseding the AirPods 4" behavior described in the issue.

What changed

TrayIconManager now keeps a small per-device registry (keyed by Bluetooth address) instead of one status string:

• updateDeviceBattery(key, name, status) upserts a device's entry and re-renders the tooltip.
• The tooltip lists every known device, active device first — with a single device the tooltip text is unchanged from before, so nothing moves for the common case.
• The icon percentage is driven only by the active device (the one with the AACP connection).
• A device's entry is removed only when that device disconnects, never by another device's update.

main.cpp wiring:

• Battery updates are recorded under the device's address together with its name; disconnect events (bluezDeviceDisconnected fires per device) remove exactly that device's entry.
• When the AACP connection switches to another device, DeviceInfo is reset so the new device doesn't inherit the previous device's name/battery in the UI. The previous device's last-known status stays visible in the tray until it actually disconnects.
• While an AACP connection is up, BLE broadcasts are ignored: the live connection is authoritative for battery/ear state, and an IRK-matched broadcast can belong to another paired device (this is the override the issue reporter observed).
• The BlueZ device name is used as the tray label until the AACP metadata packet provides the canonical name, so entries are labeled correctly from the first battery update.

Result

Hovering the tray icon with two connected devices now shows e.g.:

AirPods Pro 2: Left: 100%, Right: 100%, Case: 87%
AirPods 4: Left: 89%, Right: 89%, Case: 45%

With one device connected the tooltip is identical to current behavior (Battery Status: Left: …).

Notes / limitations

• The app still opens a single AACP (L2CAP) socket at a time, so the non-active device shows its last-known values rather than live updates; making the whole app truly multi-connection is a much bigger refactor and feels like a separate discussion (as is the "one tray circle per device" idea from the issue).
• Compile-verified against the CI toolchain (Ubuntu 24.04, Qt 6, cmake -G Ninja). I'd appreciate a hands-on test from someone with two sets of AirPods — @GarrettGR's setup from the issue is exactly the scenario this targets.