User preferences (theme, view mode, show empty) are lost when browser cache is cleared

[rogercrocha]

Problem

All user preferences set in the Settings modal — including theme, color mode (light/dark),
cellar view (cards/list/grid/table), and filter defaults — are stored exclusively in
localStorage. This means they are lost whenever the user clears browser cache or cookies,
or switches to a different browser/device.

This is particularly noticeable for multi-user setups, where each user expects their own
persistent preferences.

Context

This issue became apparent while working on PR #17, which adds a "Show out-of-stock wines"
persistent toggle. The toggle was implemented using localStorage following the same pattern
as the existing preferences — only to discover that the root problem is shared across all
settings.

Suggested solution

Implement a server-side user_preferences table in the SQLite database, keyed by username.
Add GET/POST endpoints (e.g. /api/preferences) to load and save preferences per user.
On page load, fetch preferences from the server and use them as the source of truth instead
of localStorage.

This would make all existing preferences (and future ones) truly persistent across browsers,
devices, and cache clears.

Affected preferences

• Theme (palette)
• Color mode (system / dark / light)
• Cellar view mode (cards / list / grid / table)
• Advanced filter as default
• Show out-of-stock wines (added in PR feat: show out-of-stock wines with ribbon badge and persistent setting #17)
• Table sort column and direction

[xenofex7]

Thanks for flagging this, and for the precise write-up. You're right that this is a shared root cause across all the settings, not specific to the show-empty toggle.

One design note we want to get right before implementing: in the default Home Assistant add-on deployment (Ingress) there is no authenticated user, so a strictly per-username table wouldn't apply there. The plan is a server-side preferences store that is shared per instance by default and keyed per user only when AUTH_ENABLED=true. The server will also need to inject the saved theme into the initial render to avoid reintroducing a flash of unstyled content (the theme is currently applied synchronously from localStorage in the document head).

I've added this to the roadmap (UI & Personalization). Keeping the issue open to track it.

[xenofex7]

Quick follow-up: v1.11.0 is out and ships your out-of-stock toggle (#17) - thanks again for that!

On this issue itself: we definitely want to do it, but as a deliberate, larger change rather than a quick patch, so it's planned for a later release rather than the next one. The shape we're aiming for:

• A server-side preferences store in SQLite - shared per instance by default, and keyed per user only when AUTH_ENABLED=true. That way it also works in the default Home Assistant add-on (Ingress) setup, where there is no authenticated user.
• The server injects the saved theme into the initial render, so we don't reintroduce a flash of unstyled content (the theme is currently applied synchronously from localStorage in the document head).
• localStorage stays as a fast write-through cache; the database becomes the source of truth.
• Covers the existing prefs (theme, colour mode, view mode, filter defaults, show-empty, table sort) and any future ones.

It's on the roadmap under UI & Personalization and we'll keep this issue open to track it. If you'd like to take a crack at it, happy to align on the design first so the no-auth case and the FOUC handling are covered - otherwise we'll pick it up in a later cycle.