feat: tray, window-state, sqlite cache, decrypt worker

System tray (desktop)
- tauri tray-icon feature + tray with menu (Öffnen/Ausblenden/Beenden)
- Left-click toggles main window; right-click shows menu
- JS emits tray-unread-update event, Rust mirrors into tooltip +
  macOS dock badge via set_badge_label
- ConversationsContext wires totalUnread → tray

Window state persistence
- tauri-plugin-window-state (desktop-only target guard)
- Auto-restore size/position/maximized between restarts

Local SQLite message cache
- tauri-plugin-sql hydration of conversation view on mount
- persistMessages after each refresh, deleteCachedMessage on realtime
  DELETE, pruneCache keeps latest 1000 per conversation
- Stores plaintext only (same trust boundary as stronghold device
  key; cache never leaves the device, E2EE w.r.t. server unchanged)

Web Worker for decryption
- workers/decrypt.worker.ts runs crypto_secretbox_open_easy + utf-8
  decode off the main thread with its own libsodium instance
- lib/decryptWorker.ts is a request/response wrapper with inline
  fallback when Worker spawn fails
- shared decryptMessages accepts aeadBatchDelegate so key lookup
  stays on the main thread while the AEAD loop offloads

Build fix
- Enable tauri tray-icon feature
- Import Listener + Manager traits, clone tray handle for the
  event listener, conditional icon attach

apps/desktop/src-tauri/Cargo.lock

@@ -690,6 +690,7 @@ dependencies = [
  "tauri-plugin-sql",
  "tauri-plugin-stronghold",
  "tauri-plugin-updater",
+ "tauri-plugin-window-state",
 ]
 
 [[package]]
@@ -5617,6 +5618,21 @@ dependencies = [
  "zip 4.6.1",
 ]
 
+[[package]]
+name = "tauri-plugin-window-state"
+version = "2.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "73736611e14142408d15353e21e3cca2f12a3cfb523ad0ce85999b6d2ef1a704"
+dependencies = [
+ "bitflags 2.11.1",
+ "log",
+ "serde",
+ "serde_json",
+ "tauri",
+ "tauri-plugin",
+ "thiserror 2.0.18",
+]
+
 [[package]]
 name = "tauri-runtime"
 version = "2.10.1"

apps/desktop/src-tauri/Cargo.toml

@@ -14,7 +14,7 @@ crate-type = ["staticlib", "cdylib", "rlib"]
 tauri-build = { version = "2", features = [] }
 
 [dependencies]
-tauri = { version = "2", features = ["devtools"] }
+tauri = { version = "2", features = ["devtools", "tray-icon"] }
 tauri-plugin-notification = "2"
 tauri-plugin-sql = { version = "2", features = ["sqlite"] }
 tauri-plugin-stronghold = "2"
@@ -25,6 +25,7 @@ serde_json = "1"
 [target."cfg(not(any(target_os = \"android\", target_os = \"ios\")))".dependencies]
 tauri-plugin-global-shortcut = "2"
 tauri-plugin-updater = "2"
+tauri-plugin-window-state = "2"
 
 [features]
 # This feature is used for production builds or when `devPath` points to the filesystem

apps/desktop/src-tauri/capabilities/default.json

@@ -9,6 +9,11 @@
     "notification:allow-notify",
     "notification:allow-is-permission-granted",
     "notification:allow-request-permission",
+    "sql:default",
+    "sql:allow-load",
+    "sql:allow-execute",
+    "sql:allow-select",
+    "sql:allow-close",
     "global-shortcut:allow-register",
     "global-shortcut:allow-unregister",
     "global-shortcut:allow-is-registered",

apps/desktop/src-tauri/src/lib.rs

@@ -1,3 +1,50 @@
+#[cfg(not(any(target_os = "android", target_os = "ios")))]
+use tauri::{
+    menu::{Menu, MenuEvent, MenuItem, PredefinedMenuItem},
+    tray::{MouseButton, MouseButtonState, TrayIconBuilder, TrayIconEvent},
+    AppHandle, Listener, Manager,
+};
+
+#[cfg(not(any(target_os = "android", target_os = "ios")))]
+use serde::Deserialize;
+
+// Payload for the `tray-unread-update` event the JS layer emits whenever the
+// aggregate unread-count changes. 0 hides the badge / resets the tooltip;
+// non-zero sets a count indicator.
+#[cfg(not(any(target_os = "android", target_os = "ios")))]
+#[derive(Deserialize)]
+struct TrayUnreadPayload {
+    count: u32,
+}
+
+#[cfg(not(any(target_os = "android", target_os = "ios")))]
+fn show_main_window(app: &AppHandle) {
+    if let Some(win) = app.get_webview_window("main") {
+        let _ = win.show();
+        let _ = win.unminimize();
+        let _ = win.set_focus();
+    }
+}
+
+#[cfg(not(any(target_os = "android", target_os = "ios")))]
+fn hide_main_window(app: &AppHandle) {
+    if let Some(win) = app.get_webview_window("main") {
+        let _ = win.hide();
+    }
+}
+
+#[cfg(not(any(target_os = "android", target_os = "ios")))]
+fn handle_menu_event(app: &AppHandle, event: MenuEvent) {
+    match event.id.as_ref() {
+        "tray-show" => show_main_window(app),
+        "tray-hide" => hide_main_window(app),
+        "tray-quit" => {
+            app.exit(0);
+        }
+        _ => {}
+    }
+}
+
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
     let mut builder = tauri::Builder::default()
@@ -13,12 +60,91 @@ pub fn run() {
             .build(),
         );
 
-    // Global shortcut + updater plugins are desktop-only (no mobile support).
+    // Global shortcut + updater + window-state plugins are desktop-only
+    // (no mobile support — mobile windows are OS-managed).
     #[cfg(not(any(target_os = "android", target_os = "ios")))]
     {
         builder = builder
             .plugin(tauri_plugin_global_shortcut::Builder::new().build())
-            .plugin(tauri_plugin_updater::Builder::new().build());
+            .plugin(tauri_plugin_updater::Builder::new().build())
+            .plugin(tauri_plugin_window_state::Builder::new().build());
+    }
+
+    #[cfg(not(any(target_os = "android", target_os = "ios")))]
+    {
+        builder = builder.setup(|app| {
+            // Tray icon with a minimal menu. Left-click toggles window
+            // visibility; right-click shows the menu. Badge / tooltip updates
+            // come from the JS side via `tray-unread-update` events.
+            let show = MenuItem::with_id(app, "tray-show", "Öffnen", true, None::<&str>)?;
+            let hide = MenuItem::with_id(app, "tray-hide", "Ausblenden", true, None::<&str>)?;
+            let sep = PredefinedMenuItem::separator(app)?;
+            let quit = MenuItem::with_id(app, "tray-quit", "Beenden", true, None::<&str>)?;
+            let menu = Menu::with_items(app, &[&show, &hide, &sep, &quit])?;
+
+            let mut tray_builder = TrayIconBuilder::with_id("chatapp-tray")
+                .menu(&menu)
+                .show_menu_on_left_click(false)
+                .tooltip("ChatApp")
+                .on_menu_event(|app, event| handle_menu_event(app, event))
+                .on_tray_icon_event(|tray, event| {
+                    if let TrayIconEvent::Click {
+                        button: MouseButton::Left,
+                        button_state: MouseButtonState::Up,
+                        ..
+                    } = event
+                    {
+                        let app = tray.app_handle();
+                        if let Some(win) = app.get_webview_window("main") {
+                            if win.is_visible().unwrap_or(false) {
+                                let _ = win.hide();
+                            } else {
+                                let _ = win.show();
+                                let _ = win.set_focus();
+                            }
+                        }
+                    }
+                });
+
+            // `default_window_icon` returns Option<&Image>; only attach if
+            // we actually have one bundled (should always be true via the
+            // tauri.conf.json icon list, but guard to stay typesafe).
+            if let Some(icon) = app.default_window_icon() {
+                tray_builder = tray_builder.icon(icon.clone());
+            }
+
+            let tray = tray_builder.build(app)?;
+
+            // Listen for JS-side unread updates and mirror them into the tray
+            // tooltip + macOS dock badge. `tray` is cheap to clone (internal
+            // Arc) so we can move it into the listener closure directly.
+            let tray_handle = tray.clone();
+            let badge_window = app.get_webview_window("main");
+            app.listen("tray-unread-update", move |event| {
+                let Ok(payload) = serde_json::from_str::<TrayUnreadPayload>(event.payload())
+                else {
+                    return;
+                };
+                let tooltip = if payload.count == 0 {
+                    "ChatApp".to_string()
+                } else {
+                    format!("ChatApp · {} neu", payload.count)
+                };
+                let _ = tray_handle.set_tooltip(Some(tooltip));
+                // macOS dock badge. `set_badge_label` is macOS-only but the
+                // call is a no-op on other platforms so we don't need a cfg.
+                if let Some(win) = badge_window.as_ref() {
+                    let badge = if payload.count == 0 {
+                        None
+                    } else {
+                        Some(payload.count.to_string())
+                    };
+                    let _ = win.set_badge_label(badge);
+                }
+            });
+
+            Ok(())
+        });
     }
 
     builder