🟡 Flag unreliable battery readings — "Unknown" capacity on home, warning on insights (#94)

[almothafar]

What

On devices whose charge counter is unreliable — notably certain Kirin/HiSilicon chipsets that report a small fixed µAh regardless of actual capacity — the home screen showed a bogus Capacity (e.g. 855 mAh) and the insights screen a bogus health figure (e.g. 21% on a healthy 4000 mAh battery).

This flags those readings honestly, in the right place on each screen:

• Home (Battery details): the Capacity row shows "Unknown" + a tappable amber ⓘ instead of the misleading mAh number.
• Insights (Battery health): keeps showing the real health number + grade (reverted from an earlier "Unknown" approach), but adds a tappable amber ⚠ next to it when the reading can't be trusted.
• Both affordances open the same dialog, which explains the likely cause (a hardware/counter quirk) and the genuine edge case that the battery may be wearing out — shutdowns under load, the level collapsing near the bottom (20% behaving like 2%), faster drain — with a "consider replacing" nudge.

How

• BatteryHealthTracker.isBatteryReadingUnreliable(context) — shared by both screens — flags when the current-full-capacity estimate falls outside 40%–115% of the user-entered design capacity, backed by a pure, unit-tested isEstimateImplausible(currentFullMah, designMah) helper. (Home batteryDO.getCapacity() and insights health both derive from the same getBatteryCapacity() estimate, so the two screens always agree.)
• BatteryDetailsFragment: the capacity value cell gets a compound info icon + click → dialog, only when unreliable.
• BatteryInsightsActivity: updateHealthData() always renders the resolved figure; toggles the warning icon on/off by the same check.
• New ic_warning_amber (insights) + existing ic_info_amber (home); generic battery_reading_unreliable_* strings, EN + Arabic drafts (pending maintainer review).

Notes

• The 40% floor means a genuinely worn battery reading below 40% is also flagged — the honest outcome, since we can't reliably distinguish a broken counter from a dying cell.
• A healthy counter reports ≈ design at every charge level, so healthy devices never trip this.
• Because the detection reads the live estimate, on this fixed-µAh phone it only reads implausible above ~44% charge — best tested with the battery above ~50%.
• Unit tests cover the helper (incl. the real 852-vs-4000 device case); testDebugUnitTest + assembleDebug green; installed on the Mate 10 Pro.

Closes #94