Localize missing Appearance settings strings

[digitalerdude]

What this PR does

Four strings under Settings → Appearance ("Sky behind cards" and its
caption, "Card transparency" and its caption) were added to
SettingsView.swift's appearanceCard but never made it into
Strand/Resources/Localizable.xcstrings, so every non-English locale fell
back to the raw English source text instead of showing a translation.

Adds de, es, fr, it, pt-PT, zh-Hans, and zh-Hant entries for
all four strings, reusing existing catalog terminology (e.g. "Frecuencia
cardíaca"/"心率" for Heart Rate, "Fondo según el ciclo del día" for the
day-cycle background) so they read consistently with neighboring rows.

Also includes an unrelated one-line CI fix: ReadinessChecklistCard.lead
in HealthView.swift was typed LocalizedStringKey? but
fitnessReadyLead() returns an already-localized String (via
String(localized:)), which broke the macOS build. Retyped to String?
(the only usage is Text(lead), which accepts both). This was a
pre-existing break from commit 75a096a (PR #81), not caused by this
branch, but needed fixing to get CI green here.

Note: pt-PT entries in this catalog are marked needs_review throughout
(existing entries mix in Spanish words), and the four new ones follow that
same convention — worth a native pt-PT pass over the whole file at some
point.

Type of change

• Bug fix
• New feature
• Refactor / cleanup
• Documentation
• CI / tooling

(Closest fit is "Documentation" for the string-catalog content; the
HealthView.swift change is a minimal, unrelated type fix needed for CI.)

How it was tested

• Localizable.xcstrings: validated as JSON and confirmed all four keys
  carry complete localization sets via a Python script.
• HealthView.swift: built locally with xcodegen generate +
  xcodebuild -project Strand.xcodeproj -scheme Strand -destination "generic/platform=macOS" ARCHS="x86_64 arm64" ONLY_ACTIVE_ARCH=NO build
  — BUILD SUCCEEDED.

Checklist

• Swift package tests pass for any package I touched (swift test in Packages/<name>) — N/A, no package touched
• Android unit tests pass if I touched android/ — N/A, not touched
• No new build warnings introduced
• UI changes use only StrandDesign tokens — no hardcoded colors, fonts, or spacing — N/A, no UI code changed
• No hardcoded hex frame bytes; protocol facts live in the schema / decoders — N/A
• Follows the conventions in docs/CONTRIBUTING.md
• I did not commit generated output (Strand.xcodeproj/) or any secrets/keystores

Related issues

None

[ryanbr]

Merged — thank you! This was a clean, well-scoped fix: the four Appearance strings ("Sky behind cards" / "Card transparency" and their captions) really were missing from the catalog, so non-English users were seeing raw English there. Nice catch.

Appreciated the care on the details too — reusing the existing catalog terminology so the rows read consistently with their neighbours, keeping it purely additive, and flagging the pt-PT needs_review convention rather than pretending it's final. (That whole-file native pt-PT pass is a good idea for down the line.)

The HealthView.swift type fix you mentioned had already landed on main via #132, so only the localization content came through the merge — exactly as intended. Thanks again for contributing.