SuperSearch v0.1.10

Add Settings window: accent color, extension folder install (v0.1.10)

New decorated preferences window (open_settings_window), separate from the
frameless palette overlay — toggles macOS Dock/activation policy while open,
hides (not destroys) on close to preserve state.

- accent_color setting overrides the built-in amber identity; applied via
  theme.ts:applyAccent() and live-repainted through settings-changed events.
- Native folder picker for installing an extension from a directory.
- Bump crate/bundle version to 0.1.10 (tauri.conf.json + Cargo.toml).