Add disconnect/uninstall for persistent sessions

- Server: Add DELETE /api/sessions/:id endpoint to disconnect agents
- Server: SessionManager.disconnect_session() sends Disconnect message
- Agent: Handle ADMIN_DISCONNECT to trigger uninstall
- Agent: Add startup::uninstall() to remove from startup and schedule exe deletion
- Dashboard: Add Disconnect button in Access tab machine details
- Dashboard: Add Chat button for persistent sessions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

agent/src/startup.rs

@@ -134,6 +134,49 @@ pub fn remove_from_startup() -> Result<()> {
     Ok(())
 }
 
+/// Full uninstall: remove from startup and delete the executable
+#[cfg(windows)]
+pub fn uninstall() -> Result<()> {
+    use std::ffi::OsStr;
+    use std::os::windows::ffi::OsStrExt;
+    use windows::Win32::Storage::FileSystem::{MoveFileExW, MOVEFILE_DELAY_UNTIL_REBOOT};
+
+    info!("Uninstalling agent");
+
+    // First remove from startup
+    let _ = remove_from_startup();
+
+    // Get the path to the current executable
+    let exe_path = std::env::current_exe()?;
+    let exe_path_str = exe_path.to_string_lossy();
+
+    info!("Scheduling deletion of: {}", exe_path_str);
+
+    // Convert path to wide string
+    let exe_wide: Vec<u16> = OsStr::new(&*exe_path_str)
+        .encode_wide()
+        .chain(std::iter::once(0))
+        .collect();
+
+    // Schedule the file for deletion on next reboot
+    // This is necessary because the executable is currently running
+    unsafe {
+        let result = MoveFileExW(
+            PCWSTR(exe_wide.as_ptr()),
+            PCWSTR::null(),
+            MOVEFILE_DELAY_UNTIL_REBOOT,
+        );
+
+        if result.is_err() {
+            warn!("Failed to schedule file deletion: {:?}. File may need manual removal.", result);
+        } else {
+            info!("Executable scheduled for deletion on reboot");
+        }
+    }
+
+    Ok(())
+}
+
 #[cfg(not(windows))]
 pub fn add_to_startup() -> Result<()> {
     warn!("Startup persistence not implemented for this platform");
@@ -144,3 +187,9 @@ pub fn add_to_startup() -> Result<()> {
 pub fn remove_from_startup() -> Result<()> {
     Ok(())
 }
+
+#[cfg(not(windows))]
+pub fn uninstall() -> Result<()> {
+    warn!("Uninstall not implemented for this platform");
+    Ok(())
+}