[1.4] core: frontend: App: Add battery information widget

[patrickelectric]

Battery voltage and current as a top bar widget.

Cherry-pick of #4390
Fix #4389

[github-actions]

Automated PR Review

0. Summary

• Verdict: MINOR SUGGESTIONS ✏️

Cherry-pick of #4390 to 1.4-dev. Adds a Battery top-bar widget that reads SYS_STATUS.voltage_battery / current_battery from the MAVLink store and renders them in the tray. Also consolidates the "main CPU/SoC/CCD temperature" lookup into a new cpu_temperature getter on the system-information store and updates Cpu.vue, HealthTrayMenu.vue, and SystemCondition.vue to use it. SYS_STATUS is already polled globally by MavlinkUpdater.vue, so no extra subscription is required.

6. Code Quality & Style

• 6.1 [nit] core/frontend/src/widgets/Battery.vue:41,48 — the MAVLink invalid sentinels 65535 (voltage) and -1 (current) are magic numbers. Lift them into named constants (e.g. SYS_STATUS_VOLTAGE_INVALID = 0xFFFF, SYS_STATUS_CURRENT_INVALID = -1) or add a short comment referencing the MAVLink SYS_STATUS spec so a future reader does not have to grep the protocol to know why those exact values are ignored. The pre-existing HealthTrayMenu.vue battery lines do not check these sentinels at all, so the new widget is already an improvement — worth locking in with a name.
• 6.2 [nit] core/frontend/src/widgets/Battery.vue:38,45 — mavlink_store_get returns unknown. The as number cast is immediately followed by an === undefined guard, which contradicts the cast (an actual number cannot be undefined). Consider typing the local as number | undefined (as number | undefined) so the guard reads honestly.

5. UI / UX

• 5.1 [nit] core/frontend/src/widgets/Battery.vue:57-59 vs core/frontend/src/widgets/Cpu.vue:110-112 — the Battery card uses padding-left/right: 8px, whereas the neighboring CPU widget uses 4px. Not a bug, but the two cards sit side-by-side in the tray and the asymmetric horizontal padding is visible. Aligning them would keep the tray visually consistent.
• 5.2 [nit] core/frontend/src/widgets/Battery.vue — no visual affordance for the two failure modes (autopilot offline vs autopilot reports "no measurement"): both render Loading.. forever. Not required for this PR, but a subtle icon color change or a tooltip differentiating "waiting for data" from "unsupported by autopilot" would help users diagnose why a value never appears.

8. Documentation

• 8.1 [nit] core/frontend/src/store/system-information.ts:107-112 — new cpu_temperature getter would benefit from a one-line comment explaining why cpu, soc, and ccd are the accepted substrings (Raspberry Pi reports cpu_thermal/soc, x86 AMD reports Tccd, etc.), since the substrings are otherwise unmotivated. Optional.

Generated by PR Review Bot. This is advisory, a human reviewer must still approve.

[joaoantoniocardoso]

tested