Clarify phone heart-rate broadcast copy

[kavemang]

What

Clarifies the Android Data Sources copy for the phone heart-rate broadcast feature.

Why

The card could read like a required strap setting even for users whose WHOOP/watch already broadcasts heart rate directly to another device. The updated copy explains that this is only for making the phone rebroadcast live strap HR as a standard Bluetooth HR sensor, and that users can leave it off when their wearable already handles HR broadcasting natively.

It also fixes the enabled warning to say the phone is advertising continuously, not the strap.

Closes #159.

Validation

• ./gradlew :app:compileFullDebugKotlin

[ryanbr]

The Android copy is accurate and this closes #159 cleanly — I confirmed the third change ("This phone is advertising" instead of "Your strap is advertising") is a real correctness fix, since it's the phone that acts as the BLE HR peripheral. Safe to merge on its own. One thing missing though: it's one-sided.

Missing: the iOS twin card

Strand/Screens/DataSourcesView.swift:784 is the exact same "Broadcast HR from this phone" card and didn't get the same clarifications:

• Subtitle (line 787) is identical and still lacks your new "if your strap or watch already broadcasts HR directly to another device, leave this off" sentence → needs change Import v8.2.2 snapshot (upstream catch-up + board wave; ports PRs #1035/#1036 + BLE/readiness fixes) #1.
• Footnote (line 799) is the exact old text you rewrote — "Acts as a standard Bluetooth heart-rate strap. Pair NOOP from your treadmill, bike or app to see your strap's heart rate there." → needs change Fork CI: staging-release APK, versioned artifact names, R8-optimised release #2.
• Change Revert release to unminified (R8 minify crashes at runtime); keep staging-release + versioned names #3 (strap → phone) has no iOS counterpart to fix — iOS shows a dynamic status instead of a static warning (statusNote / "N devices reading your heart rate" / "Sharing X bpm. Waiting…"), so it never had the "strap is advertising" error. Nothing to do there.

One heads-up for the iOS side

iOS copy is localized (String(localized:) → .xcstrings), so mirroring these two lines touches the string catalog, and the German translations (#326) will fall back to English until updated. Android's strings are inline literals, so this PR had no such cost — which is why the two platforms need slightly different handling.

None of this blocks the Android change. Just flagging that the #159 fix is only half-applied until the iOS DataSourcesView card gets the same subtitle + footnote copy — worth either folding in here or tracking as a quick follow-up.

[kavemang]

Superseded by #508, which carries the identical change from the corrected issue-oriented branch.