feat(mobile): align upgrade prompts with desktop

[DIYgod]

Summary

• align mobile 402 upgrade handling with desktop for subscription, list, and import flows
• keep translation limits silent while showing summary upgrade state inline in the AI Summary card
• sync plan copy and CTA rendering with backend payment config

Testing

• pnpm --dir apps/mobile run typecheck
• pnpm --dir packages/internal/store run typecheck
• pnpm exec eslint apps/mobile/src/App.tsx apps/mobile/src/lib/error-parser.ts apps/mobile/src/modules/feed/FollowFeed.tsx apps/mobile/src/modules/list/FollowList.tsx apps/mobile/src/modules/settings/routes/ManageList.tsx apps/mobile/src/modules/settings/routes/Plan.tsx apps/mobile/src/modules/settings/utils.ts 'apps/mobile/src/screens/(modal)/ListScreen.tsx' packages/internal/store/src/modules/summary/store.ts
• pnpm --dir apps/mobile run e2e:doctor
• local follow-server + iOS simulator self-test for subscription-limit modal and summary inline upgrade card

Screenshots

• Subscription limit modal: /tmp/folo-subscription-limit-prompt.png
• Summary inline upgrade card: /tmp/folo-summary-current.png
• Plan screen: /tmp/folo-plan-screen.png
• Plan lower section: /tmp/folo-plan-screen-lower.png

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Distinguish empty summaries from quota failures

SummaryResponse is string | null, but this guard uses a falsy check, so a valid empty-string summary ("") is treated as a payment-limit failure and converted into a synthetic 402 error. In that case the UI will incorrectly show an upgrade-required state (and mark generation as error) instead of handling the response as an empty summary. Restrict this branch to null/undefined (for example summary.data == null) so only missing payloads trigger the upgrade path.

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