feat(i18n): extract settings & account pages (batch 3)

[JamieRuderman]

Summary

Batch 3 of Phase 4 extraction: the Settings & Account pages — completing the settings/account area that OptionsPage and ProfilePage started. 34 keys (a new settings.* group + two reusable common.* keys), fully translated to ja/de/es.

Files: SettingsPage, AccountPage, SecurityPage, NotificationsPage + NotificationsMode, and the remaining hardcoded strings in ProfilePage (Profile title, Gravatar caption, Email / Member-since labels, Email Language, Account deletion).

Stacked on i18n/extract-notices (#1153) to inherit the parser and plural-check fixes. The diff here is settings-only. Retarget order once things merge: #1152 → #1153 → this.

Notes

• Key reuse — settings.profile, settings.security, settings.notifications each label both a nav item and the corresponding page title, so they're defined once and shared. Added common.save / common.saving (used by the webhook form) as reusable keys alongside the existing common.areYouSure.
• Sentence-case vs title-case — "Sign out everywhere" (heading) and "Sign Out Everywhere" (button) are separate English keys; in ja/de/es they translate identically (the casing distinction doesn't map), which is expected.
• Embedded links — the Gravatar caption and the webhook help text each end in a link; the sentence and the link label are separate t() calls rather than <Trans>, keeping the link (gravatar.com., Docs) intact. The example webhook URL placeholder is left untranslated (it's a sample URL).
• No plurals or interpolation in this batch.

Verification

• i18n:check passes — 4 locales × 3 namespaces, no missing/dead keys, no empty English.
• tsc clean; production build passes.

Untranslated strings elsewhere still fall back to English.

🤖 Generated with Claude Code

[JamieRuderman]

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Add spacing before the Gravatar link

When the UI language is German or Spanish, settings.gravatarEdit ends in an ordinary word (bitte or visita), but this link is placed immediately after the translated expression without explicit whitespace. JSX does not preserve the formatting newline here, so the caption renders as bittegravatar.com. or visitagravatar.com.; add {' '} before the link, as the webhook caption does.

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