chore(l10n): remove dead localization keys from non-en arb files

[ethicnology]

Thanks to @bsn21m

Removed 10 keys (and their @metadata) that exist in translation files but not in the app_en.arb template, so no getter is generated and no Dart code references them:

• autoswapWarningTriggerAmount, autoswapWarningBaseBalance
• homeLegacyStorageWithNoBackupTitle, homeLegacyStorageWithNoBackupDescription
• homeLegacyStorageTitle, homeLegacyStorageDescription
• legacyStorageWarningBackupNow, legacyStorageWarningLater
• errorReportingMigrationSubtitle, transactionSwapOpenWithin24Hours

[claude]

Claude finished @ethicnology's task in 2m 6s —— View job

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Review: PR #2285 — remove dead localization keys

• Read the diff and removed keys
• Verify removed keys are truly absent from app_en.arb
• Verify no Dart code references the removed keys
• Check ARB files remain valid JSON
• Post review summary

Summary

LGTM ✅ — This is a safe, correct cleanup. No bugs, security issues, or regressions found.

The PR removes 10 keys (plus their @metadata) from the 25 non-English .arb files. I verified each correctness concern:

Check	Result
All 10 keys absent from localization/app_en.arb (the template that drives codegen)	✅ confirmed — 0 matches
Any Dart code in lib/ references the removed getters	✅ none — 0 matches
Keys fully removed from every translation file (searched all of localization/)	✅ 0 remaining occurrences
Removed keys were not the last entry in any file (trailing-comma / invalid-JSON risk)	✅ tail of each file ends on an unrelated key with no dangling comma

Why this is safe: Flutter's gen_l10n generates getters from the template (app_en.arb) only. Keys present in translation files but missing from the template produce no getter and are silently ignored, so they are genuinely dead weight. Removing them has zero runtime impact and reduces noise for translators.

Minor observations (non-blocking):

• The PR description lists 10 keys, and that's exactly what was removed — accurate.
• Worth confirming none of these strings are slated for re-introduction into app_en.arb in an in-flight feature branch (e.g. the homeLegacyStorage* / legacyStorageWarning* group looks like it was a paired feature). If so, the translations would need to be re-added later. Not a defect in this PR — just a coordination note.

Nice cleanup. 👍