fix(terminal): persist Ctrl+/- font zoom so it survives option refreshes

[tcezarl]

Persist terminal font zoom (Ctrl +/- / Ctrl+wheel) so it survives option refreshes

Problem

Zooming the terminal with Ctrl +/- or Ctrl+wheel changes the font size for
~30–60 s and then snaps back to the configured size.

changeTerminalFontSize() only mutates terminal.options.fontSize and
terminalFontSizeRef.current; it never persists. The "update terminal options
individually" effect in Terminal.tsx (deps include isFitted,
terminalDefaults, hostConfig.terminalConfig) re-runs on the WebSocket
keepalive / refit / reconnect cycle and unconditionally reassigns
terminal.options.fontSize = config.fontSize, discarding the zoom.

Fix

Persist the zoom level per host in localStorage
(terminal_fontsize_host_<hostId>, mirroring the existing
terminal_theme_host_<hostId> pattern) and have the terminal-option effects
prefer that override:

• changeTerminalFontSize() writes the new size to localStorage.
• The creation effect and the "update options" effect read the override and
  apply it instead of config.fontSize.
• If the configured font size itself changes (user edits it in Settings /
  host config), the override is cleared so the new configured value wins.

All storage access is wrapped in try/catch (private mode / disabled storage
falls back to the configured size).

Testing

• Zoom in, wait past the keepalive interval — size holds.
• Reload — size persists.
• Change Font Size in Connection Defaults — override is dropped, new value applies.
• Storage disabled — no errors, behaves as before (transient zoom only).

[ZacharyZcR]

This needs changes before merge. The persisted value stores only the zoomed font size, not the configured size it was derived from. If a user zooms a host, closes the terminal, changes Connection Defaults while that terminal is unmounted, and reopens it, lastConfiguredFontSizeRef initializes to the new configured value and the old localStorage override still wins forever. The claimed “configured font size change clears the override” only works while this component remains mounted. Store the configured/base size alongside the override (or use another design that can invalidate stale overrides on mount) and add a regression test for that closed-terminal settings-change path.

Also avoid terminal_fontsize_host_undefined: quick-connect terminals do not necessarily have a host id, so unrelated quick-connect sessions currently share one persisted override. Finally, please retarget/rebase this onto the active dev-2.8.0 branch; the current main base produces an unrelated multi-file diff against development.