fix: stop startup settings hydration from deleting API keys, fix stuc… #4730

Originally written by @ccantynz-alt on GitHub.
Imported from https://github.com/ccantynz-alt/voxlen/pull/71

…k shortcut

API keys not persisting across restarts: startup hydration (loading settings.json / backend settings back into the store) went through the same updateSettings action that also schedules a write-back persist cycle. If the keychain-backed API key hadn't finished loading into the store by the time that 500ms debounce fired, its write-or-delete keychain logic saw an empty key and deleted the one already stored — actively erasing it, not just failing to show it. Added a separate hydrateSettings action that updates the store without scheduling a persist, and switched both startup load paths (settings.json and backend get_settings) to use it.

Global shortcut (Ctrl+Shift+D) not working: the toggle handler only treated idle/paused as "start" conditions, so once dictation status got stuck at "error" (e.g. from a mic failure), pressing the shortcut fell into the stop branch and silently no-opped forever after. Added the missing "error" case, matching DictationPanel's own toggle handler. Also split shortcut registration so each of the four shortcuts registers independently — a single conflict (e.g. taken by another app) no longer silently prevents the rest from registering — and surfaced registration failures via toast + console.error instead of swallowing them under the same catch used for "not running in Tauri".