Adds an Automations nav entry + page to the video side. The automation engine is
app-wide, so this surfaces the SAME system automations the music side runs — filtered
to is_system, EXCLUDING Refresh Beatport Cache and any user/playlist-pipeline ones.
Reads the shared /api/automations (no music imports), reuses the music .automation-*
card look, and supports run-now + enable toggle (system automations aren't editable).
Polls every 5s while the page is open. Frontend-only; balance clean.
Next: the library-refresh/scan automation wiring (Boulder has questions on how server
scanning works first).
