fix(ssh-config): ask each account before importing ~/.ssh/config (#557)

[kipavy]

Fixes #557.

The SSH Config Sync plugin imported this machine's ~/.ssh/config hosts, keys and identities into the Personal vault of whichever account was signed in. That included a second, unrelated account (e.g. a customer's self-hosted account) used on the same workstation.

What changes

• Before its first sync on an account, the plugin shows a notification banner: "Import N hosts from this computer's ~/.ssh/config into this account's Personal vault? Their SSH keys are imported too." with Import / Don't import.
• The answer is stored as import_consent in plugin storage. Plugin storage is restored per account on sign-in and account switch, so each account answers for itself. Dismissing the banner without answering asks again next launch. No prompt when ~/.ssh/config is missing or has no usable hosts.
• Declined or unanswered accounts get no initial sync and no file watcher. A poll-interval change no longer restarts a stopped watcher. "Sync now" and the MCP sync tool refuse too.
• New settings toggle Import from this computer changes the answer: on starts sync and watcher, off stops the watcher.
• Existing accounts: an account with no stored answer but a non-empty alias_map counts as having said yes, so current users see no change after updating.
• The three settings toggle rows now share one toggleRow helper.
• Strings in all 6 locales with plural forms. Manifest 1.2.1 → 1.3.0.

Not changed

• Declining or turning the toggle off does not remove hosts and keys already imported. Users who were already hit have to delete those by hand.
• The answer is per account, not per device: saying Import on one machine means another machine signed in to the same account also imports its own ~/.ssh/config.
• Users running a marketplace-installed copy keep the old behaviour until they click Update, which needs the catalogue entry bumped after release.

Verification

• register.test.ts: 9 new tests. Forcing the gate open makes 8 of them fail.
• vitest run src/plugins/ssh-config: 34 passed. tests/pluginCatalogPublish.test.ts passes.
• tsc --noEmit clean, check-plugin-versions OK.
• Not verified in the running app (banner, toggle, account switch).