feat(start-os): name the installed web app after the server

[MattDHill]

Closes #2327

Summary

An installed StartOS web app is named after the server rather than StartOS.

RpcContext's router now serves /manifest.webmanifest itself, parsing the built manifest out of the embedded UI dir and replacing name and short_name with the hostname from AccountInfo. Every other context keeps falling through to the static file, so init and diagnostic mode still resolve the manifest.

Safari does not take the Home Screen name from the manifest — it reads apple-mobile-web-app-title, which index.html hard-codes. AppComponent now keeps that tag in step with serverInfo.hostname, alongside the language subscription that was already there. Chrome and Chromium desktop refresh an installed app's name from the manifest on their own; iOS needs the app removed and added again, which the changelog and the docs both say.

The manifest is dropped from ngsw-config.json's prefetch group. ngsw.json pins a sha1 of the bytes the build produced, and the served body is no longer those bytes — leaving it listed would fail the service worker's hash check and take it out of service. A note in projects/start-os/AGENTS.md warns the next person off putting it back.

Server Name dialog

The dialog now lists what the name is used for, since a rename reaches further than the .local address alone:

• the server's address
• every installed service's local address (services are served at <name>.local:<port>)
• the browser tab and the installed app's name
• SSH and system logs

Five new strings, translated across all five dictionaries. docs/src/server-name.md gains the same facts.

Verification

• FMT_NATIVE=1 make start-core-format-check
• npm run check:i18n
• prettier over every changed TS, JSON and Markdown file

The Rust build and the web typechecks are left to CI.