Show in-app web apps only to users who already have them connected #5423

Summary

The embedded web apps should appear only for people who already have one connected. Everyone else shouldn't see the feature at all. The people who do have them get a notice about the 31 August removal.

Problem

The app offers a list of web services you can open inside it — WhatsApp, Telegram, LinkedIn, Slack, Discord, Gmail, Outlook, Instagram, X. Anyone can currently find and connect one. The feature is being removed from the app after 31 August, so new people shouldn't be picking it up, and the people already using it need to know.

What should happen

No web apps connected — the feature isn't visible anywhere in the app.

Has web apps connected — sees only the services already connected. Someone with Gmail and Discord sees Gmail and Discord, and can reconnect them if a session drops. Cannot add a service they weren't already using.

The notice — those users see a message saying the feature will be removed from the app after 31 August, apologising for the inconvenience. It stays visible rather than being dismissable.

This issue covers visibility and the notice only. It doesn't remove any code.

Acceptance criteria

• A user with no web apps connected sees no trace of the feature anywhere in the app.
• A user with web apps connected still sees them, still works normally, and can reconnect if needed.
• Those users cannot add a service they weren't already using.
• A clear notice appears for those users, naming 31 August and apologising for the inconvenience.
• The notice is translated into every language the app supports.
• Nothing breaks for existing users between now and 31 August.
• Diff coverage ≥ 80% — the implementing PR meets the changed-lines coverage gate (Vitest + cargo-llvm-cov, enforced by .github/workflows/ci-lite.yml).

Related

#5424 — sibling issue covering tiny.place. Same deadline and same shape — the two should ship together so users see one change rather than two separate disappearances.