feat: Heartbeat fuer Locks - vergessene Locks laufen nach 15 Min ab

Wenn jemand vergisst zu entsperren:
- Client laeuft -> Heartbeat alle 60s -> Lock bleibt aktiv
- Client geschlossen -> kein Heartbeat -> Lock laeuft nach 15 Min ab
- Laptop zugeklappt -> gleicher Effekt -> 15 Min -> frei

Tracking: locked_files Vec merkt sich welche Dateien wir gesperrt haben.
Heartbeat laeuft im Token-Refresh Thread mit (alle 60s Heartbeat,
alle 10 Min Token-Refresh).

Lock wird beim Oeffnen getrackt, beim Entsperren/Unmark-Offline entfernt.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -19,6 +19,7 @@ struct AppState {
     sync_engine: Mutex<Option<SyncEngine>>,
     username: Mutex<Option<String>>,
     watchers: Mutex<Vec<FileWatcher>>,
+    locked_files: Mutex<Vec<i64>>, // file IDs we have locked on server
     sync_running: Arc<Mutex<bool>>,
     sync_paths: Mutex<Vec<SyncPath>>,
 }
@@ -263,7 +264,10 @@ async fn open_cloud_file(state: State<'_, AppState>, cloud_path: String) -> Resu
 
     // Lock on server (prevents others from editing)
     match api.lock_file(file_id, "Desktop Sync Client").await {
-        Ok(_) => eprintln!("[OpenCloud] Locked on server"),
+        Ok(_) => {
+            eprintln!("[OpenCloud] Locked on server");
+            state.locked_files.lock().unwrap().push(file_id);
+        }
         Err(e) => eprintln!("[OpenCloud] Lock failed (file may be locked by someone else): {}", e),
     }
 
@@ -279,6 +283,7 @@ async fn open_cloud_file(state: State<'_, AppState>, cloud_path: String) -> Resu
 async fn unlock_file_cmd(state: State<'_, AppState>, file_id: i64) -> Result<String, String> {
     let api = state.api.lock().unwrap().clone().ok_or("Nicht eingeloggt")?;
     api.unlock_file(file_id).await?;
+    state.locked_files.lock().unwrap().retain(|&id| id != file_id);
     Ok("Datei entsperrt".to_string())
 }
 
@@ -495,17 +500,30 @@ fn start_background_sync(
         }
     });
 
-    // Token refresh every 10 minutes
+    // Token refresh (every 10 min) + Heartbeat for locks (every 60s)
     let app_hb = app.clone();
     let api_hb = api.clone();
     std::thread::spawn(move || {
         let rt = tokio::runtime::Runtime::new().unwrap();
         let mut api_mut = api_hb.clone();
+        let mut tick = 0u32;
 
         loop {
-            std::thread::sleep(Duration::from_secs(600));
+            std::thread::sleep(Duration::from_secs(10));
+            tick += 10;
             let state = app_hb.state::<AppState>();
 
+            // Heartbeat every 60 seconds for locked files
+            if tick % 60 == 0 {
+                let locked = state.locked_files.lock().unwrap().clone();
+                for file_id in &locked {
+                    let _ = rt.block_on(api_mut.heartbeat(*file_id));
+                }
+            }
+
+            // Token refresh every 10 minutes
+            if tick >= 600 {
+                tick = 0;
                 if let Ok(new_token) = rt.block_on(api_mut.refresh_token()) {
                     if let Some(ref mut api) = *state.api.lock().unwrap() {
                         api.access_token = new_token;
@@ -513,6 +531,7 @@ fn start_background_sync(
                     eprintln!("[Auth] Token refreshed");
                 }
             }
+        }
     });
 
     // File watcher: detects changes and triggers immediate sync
@@ -630,6 +649,7 @@ pub fn run() {
             username: Mutex::new(None),
             watchers: Mutex::new(Vec::new()),
             sync_running: Arc::new(Mutex::new(false)),
+            locked_files: Mutex::new(Vec::new()),
             sync_paths: Mutex::new(Vec::new()),
         })
         .on_window_event(|window, event| {