feat: SSH session persistence across app background/foreground

[ZacharyZcR]

Summary

• Adapt mobile client to server-side session persistence protocol (depends on Termix PR #594): when the app goes to background and iOS/Android kills the WebSocket, the server keeps the SSH session alive (default 30 min). On foreground return, the client sends attachSession to reattach with buffered output replay instead of creating a new SSH connection.
• Handle session lifecycle messages: sessionCreated, sessionAttached, sessionExpired (auto-fallback to fresh connect), and sessionTakenOver (multi-device graceful disconnect).
• Send explicit disconnect on component destroy to clean up server-side sessions when the user intentionally closes a terminal tab.
• Skip terminal clear and post-connection setup on reattach so the user sees continuous output without a jarring reset.

Files Changed

File	Change
app/tabs/sessions/terminal/NativeWebSocketManager.ts	Core session persistence logic — track serverSessionId, conditional attachSession vs connectToHost, new message handlers
app/tabs/sessions/terminal/Terminal.tsx	Skip terminal reset and hasReceivedData clear on reattach

Test plan

• Connect to a host → background the app for ~10s → return to foreground → verify session reattaches without terminal clear, previous output preserved
• Connect to a host → background the app → wait for server timeout (default 30 min) → return → verify graceful fallback to fresh connection
• Connect to a host → close the terminal tab → verify server-side session is destroyed (check server logs for session_destroyed)
• Connect to same host from two devices → verify second device takes over, first shows disconnect
• Connect to a host → toggle airplane mode → return → verify reconnection works (fresh connect since server lost the session)
• Verify npx tsc --noEmit shows no new errors beyond pre-existing upstream issues

Note: This PR depends on the server-side session persistence feature from Termix PR #594. Without the server changes, the client will receive no sessionCreated messages and behave identically to the current version (always fresh connectToHost).

Fixes Termix-SSH/Support#364