feat: add WebDAV cloud sync with encrypted secrets support

Add WebDAV-based settings sync for desktop app, including connection
configuration, editor settings, and optional encrypted secrets sync.
Also persist WebDAV remember-password preference across sessions.

src-tauri/src/commands/cloud_sync.rs

@@ -0,0 +1,85 @@
+use std::sync::Arc;
+
+use dbx_core::cloud_sync::{
+    apply_sync_snapshot, build_sync_snapshot, forget_webdav_password, resolve_webdav_password, save_webdav_password,
+    webdav_saved_password_status, ApplySnapshotOptions, ApplySnapshotSummary, WebDavClient, WebDavConfig,
+    WebDavPasswordStatus, WebDavSyncSummary,
+};
+use dbx_core::storage::DesktopSettings;
+use serde::{Deserialize, Serialize};
+use tauri::State;
+
+use dbx_core::connection::AppState;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct WebDavDownloadResult {
+    pub summary: WebDavSyncSummary,
+    pub editor_settings: Option<serde_json::Value>,
+    pub desktop_settings: DesktopSettings,
+    pub apply_summary: ApplySnapshotSummary,
+}
+
+#[tauri::command]
+pub async fn webdav_sync_test(state: State<'_, Arc<AppState>>, mut config: WebDavConfig) -> Result<(), String> {
+    resolve_webdav_password(&state.storage, &mut config).await?;
+    WebDavClient::new(config).test().await
+}
+
+#[tauri::command]
+pub async fn webdav_password_status(
+    state: State<'_, Arc<AppState>>,
+    config: WebDavConfig,
+) -> Result<WebDavPasswordStatus, String> {
+    webdav_saved_password_status(&state.storage, &config).await
+}
+
+#[tauri::command]
+pub async fn save_webdav_saved_password(
+    state: State<'_, Arc<AppState>>,
+    config: WebDavConfig,
+    password: String,
+) -> Result<(), String> {
+    save_webdav_password(&state.storage, &config, &password).await
+}
+
+#[tauri::command]
+pub async fn forget_webdav_saved_password(state: State<'_, Arc<AppState>>, config: WebDavConfig) -> Result<(), String> {
+    forget_webdav_password(&state.storage, &config).await
+}
+
+#[tauri::command]
+pub async fn webdav_sync_upload(
+    state: State<'_, Arc<AppState>>,
+    mut config: WebDavConfig,
+    editor_settings: Option<serde_json::Value>,
+    secrets_passphrase: Option<String>,
+) -> Result<WebDavSyncSummary, String> {
+    resolve_webdav_password(&state.storage, &mut config).await?;
+    let snapshot =
+        build_sync_snapshot(&state.storage, env!("CARGO_PKG_VERSION"), editor_settings, secrets_passphrase.as_deref())
+            .await?;
+    WebDavClient::new(config).put_snapshot(&snapshot).await
+}
+
+#[tauri::command]
+pub async fn webdav_sync_download(
+    state: State<'_, Arc<AppState>>,
+    mut config: WebDavConfig,
+    secrets_passphrase: Option<String>,
+) -> Result<WebDavDownloadResult, String> {
+    resolve_webdav_password(&state.storage, &mut config).await?;
+    let (snapshot, summary) = WebDavClient::new(config).get_snapshot().await?;
+    let apply_summary = apply_sync_snapshot(
+        &state.storage,
+        &snapshot,
+        ApplySnapshotOptions { secrets_passphrase: secrets_passphrase.as_deref() },
+    )
+    .await?;
+    Ok(WebDavDownloadResult {
+        summary,
+        editor_settings: snapshot.editor_settings,
+        desktop_settings: snapshot.desktop_settings,
+        apply_summary,
+    })
+}

src-tauri/src/commands/mod.rs

@@ -1,6 +1,7 @@
 pub mod agents;
 pub mod ai;
 pub mod app_settings;
+pub mod cloud_sync;
 pub mod connection;
 #[allow(dead_code, unused_imports)]
 mod connection_secrets;