feat(i18n): extract redux notice messages (batch 2)

[JamieRuderman]

Summary

Batch 2 of Phase 4 extraction: the redux model notice messages — the success/error/notice toasts dispatched from dispatch.ui.set({ successMessage / errorMessage / noticeMessage }) across 16 model files. 60 messages → 65 keys in the notices namespace, fully translated to ja/de/es.

Since these run in non-React model code, they call the shared i18n instance directly: i18n.t('notices:key', { ...vars, defaultValue }).

Stacked on i18n/extract-shell (#1152) because it depends on that branch's parser fix. Once #1152 merges to feature/i18n, I'll retarget this PR — the diff here is notices-only.

Highlights — the pitfalls the plan called out, handled

• Pluralization — replaced hand-rolled ternaries (device${n>1?'s were':' was'}) with i18next count plurals (_one/_other). This also fixes an English bug: the old code rendered "1 devices were…"; it now correctly says "1 device was…". Verified at runtime across locales (German inflects the verb too: "wurde" vs "wurden"; Japanese uses its single form).
• Interpolation, never concatenation — every ${name}/${email}/${error} became a {{placeholder}}; string-built messages ('Update phone error: ' + error.message) collapsed into one keyed call.
• Word order — the possessive ${who} ${plan} subscription updated (where who was 'Your' or `${email}'s`) was split into two keys (subscriptionUpdatedYours / subscriptionUpdatedOther) so each language renders possession naturally rather than forcing English 's.
• Conditional nouns — that ${isService ? 'service' : 'device'} split into two keys.
• Not translated — API/dynamic values (device names, emails, error.message) stay as runtime interpolation values.

Tooling fix (separate commit)

Made i18n:check plural-aware. Plural keys expand per-locale via CLDR (Japanese: _other only; English/German: _one+_other; Spanish also _many), so strict key-equality would wrongly flag Japanese as "missing" _one. The check now compares plural bases against each locale's own Intl.PluralRules categories.

Verification

• i18n:check passes (plural-aware) — 4 locales × 3 namespaces, no missing/dead keys, no empty English.
• tsc clean; production build passes.
• Placeholder parity verified programmatically across en/ja/de/es (zero mismatches).
• Runtime plural resolution spot-checked: count=1 vs 5 renders the correct grammatical form in every language.

🤖 Generated with Claude Code

[JamieRuderman]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Nice work!

Reviewed commit: da305b2d45

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