Add Presets section (name/frequency/voltage) to Settings page

[xr1140]

Adds a Presets section to the AxeOS Settings page that lets users save named combinations of frequency and core voltage and apply them with one click. Fully client-side — no firmware/C changes.

Tuning a Bitaxe often means switching between a few known-good frequency/voltage combos (e.g. a quiet profile vs. a performance profile). Today that requires re-typing/selecting both values every time. Presets make switching a single click.

What's included

• Save the current Frequency + Core Voltage under a name (max 5 presets).
• Apply a preset — patches the form and sends PATCH /api/system with { frequency, coreVoltage }. Since both are non-restart fields, it takes effect without a reboot.
• Edit / Delete existing presets (full CRUD).
• Export / Import presets as a JSON file, so they can be backed up and moved between browsers/devices.

Design notes

• Presets are stored in the browser via the existing LocalStorageService (key ASIC_PRESETS), mirroring how the Swarm feature already persists user data client-side. This keeps the feature entirely in AxeOS with zero device-side/NVS changes.
• Implemented inside the existing EditComponent (the Settings form), reusing its reactive form and the existing SystemApiService.updateSystem() call. No new PrimeNG modules or dependencies were added.
• Import validation rejects malformed JSON and silently caps at 5 entries.

Files changed

• main/http_server/axe-os/src/app/components/edit/edit.component.ts
• main/http_server/axe-os/src/app/components/edit/edit.component.html

Testing

• npm run build compiles cleanly (AOT type-checks component + template).
• Manually verified in the app: add/edit/delete presets, persistence across reloads, the 5-preset cap, Apply updating the Frequency/Core Voltage selects and hitting PATCH /api/system, and Export → clear → Import round-trip.
• Built www.bin and flashed via Settings → Update on a real device.

Screenshots

Notes

• Presets are browser-local (per the localStorage approach); Export/Import covers moving them between browsers.
• No API, OpenAPI spec, or firmware changes — the existing PATCH /api/system endpoint is reused as-is.