Colour themes, synced across devices (beta)

Seven themes (Spruce, Ocean, Violet, Rose, Crimson, Amber, Graphite) that
change only the brand colour, all AA in light and dark. "Same theme on all
my devices" saves the choice in the encrypted vault and adopts it after
unlocking and syncing.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src-tauri/src/main.rs

@@ -408,6 +408,26 @@ fn resolve_save(app: State<'_, App>, id: String, accept: bool) -> CmdResult<()>
     Ok(())
 }
 
+/// The colour theme and appearance saved for all the account's devices (docs/02 "App settings").
+#[derive(Serialize)]
+struct ThemeView {
+    theme: Option<String>,
+    appearance: Option<String>,
+}
+
+#[tauri::command]
+fn app_theme(app: State<'_, App>) -> CmdResult<ThemeView> {
+    let t = app.core.app_theme().map_err(err)?;
+    Ok(ThemeView { theme: t.theme, appearance: t.appearance })
+}
+
+#[tauri::command]
+fn set_app_theme(app: State<'_, App>, theme: Option<String>, appearance: Option<String>) -> CmdResult<()> {
+    app.core.set_app_theme(theme, appearance).map_err(err)?;
+    app.sync.request_sync();
+    Ok(())
+}
+
 #[tauri::command]
 fn pending_passkeys(app: State<'_, App>) -> Vec<PasskeyView> {
     app.broker.pending_passkeys()
@@ -730,6 +750,8 @@ fn main() {
             pending_saves,
             pending_passkeys,
             set_tags,
+            app_theme,
+            set_app_theme,
             sign_in_providers,
             resolve_passkey,
             resolve_save,