feat: delete machines + hide offline from settings

[bra1nDump]

Summary

Users had dead/zombie machines cluttering their machine list after daemon reauthentications (reported on Discord by ratio [CLAW]). This adds a way to clean them up without affecting session history.

• Settings → Machines: offline machines hidden by default, with a toggle to reveal them (shows count)
• Machine detail screen: new Danger Zone with a delete button, confirmation modal, navigates back on success
• Server DELETE /v1/machines/:id: removes the machine + its access keys, preserves sessions, broadcasts a new delete-machine event to all the user's connected clients
• Client sync: handles delete-machine event → removes machine from storage, drops encryption keys and machineDataKeys, guarded on local presence so stale events are no-ops

Backwards compatibility

Old clients (pre-upgrade) on the same account will receive the new delete-machine event but will safely ignore it — handleUpdate uses safeParse and drops unknown discriminants. They'll see the deleted machine disappear on next full fetch / reconnect. No hard break.

Notes for reviewer

• Machine deletion intentionally preserves past sessions — the server has no FK from Session to Machine (machineId lives in encrypted session metadata), so nothing cascades.
• AccessKeys must be deleted first because they have a composite FK to Machine — handled inside a single inTx block.
• All 10 locale files updated (en, ru, it, ja, zh-Hans, zh-Hant, ca, pl, es, pt). Polish uses proper plural rules (1, 2-4, 5+, with 11-14 special case).
• CHANGELOG bumped to v9 and changelog.json regenerated.

Test plan

• App builds and pnpm typecheck passes in both happy-app and happy-server
• Settings → machine list shows only online machines by default; toggle reveals offline ones with correct count
• Delete machine from detail screen → confirmation modal → machine vanishes from list → navigation back works
• Delete event propagates to a second device on same account (machine disappears without restart)
• Session history for deleted machine is still viewable
• Translations render correctly in at least one non-English locale (plural count)

🤖 Generated with Claude Code