feat(theme): support system light and dark themes

[Soundcreates]

Summary

• add persisted light and dark theme mappings
• add optional Follow system appearance mode using prefers-color-scheme
• expose filtered light/dark theme pickers in Appearance settings
• preserve SQL editor Same as App synchronization

Closes #649

Validation

• pnpm typecheck
• pnpm lint
• pnpm build
• cargo check --manifest-path src-tauri/Cargo.toml
• git diff --check

The repository-wide cargo fmt --check currently reports unrelated pre-existing formatting differences outside this change.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (4 files)

• src-tauri/src/config.rs
• src/components/settings/AppearanceTab.tsx
• src/contexts/ThemeProvider.tsx
• src/i18n/locales/en.json

---

The change adds persisted followSystemTheme, lightThemeId, and darkThemeId config fields with correct Rust Option-guarded merging in save_config, mirrors them through the AppConfig TS interface, wires the new pickers in AppearanceTab, and updates the ThemeProvider load/save/system-listener effects consistently. Defaults are applied correctly via DEFAULT_THEME_SETTINGS, the system matchMedia listener uses the configured light/dark IDs, and effect dependencies cover the read state with no stale-closure gaps. No security, runtime, or logic defects found in the changed lines.

---

_{Reviewed by glm-5.2 · Input: 27.7K · Output: 6.5K · Cached: 224.8K}

[debba]

Thanks a lot for this, and sorry for the timing overlap: #650 was opened by the issue author a few minutes before yours and lands the same config fields and mode switch, plus the native window chrome sync via Tauri setTheme (the Linux/GNOME CSD case discussed in #649), all 11 locales and test coverage. I've merged that one and I'm closing this to avoid two parallel implementations of the same feature.

Two things from your PR I'd genuinely like to see as follow-ups if you're up for it:

1. hydrating settings.customThemes from the loaded custom themes in ThemeProvider (feat: follow system light/dark appearance with per-mode theme selection #650 doesn't do that and it looks like a real gap);
2. defaulting followSystemTheme to true for fresh installs (no theme in config.json), keeping Static for existing configs, as raised in the [Feature]: Follow system light/dark appearance with per-mode theme selection #649 thread.

Happy to review either quickly.